chore: discount line items directly

server/src/internal/balances/utils/allocatedInvoice/compute/computeAllocatedInvoiceLineItems.ts

@@ -1,6 +1,8 @@
 import {
+	BILLING_AMOUNT_EPSILON,
 	cusEntToCusPrice,
 	InternalError,
+	type LineItem,
 	type LineItemContext,
 	orgToCurrency,
 	priceToProrationConfig,
@@ -10,6 +12,7 @@ import {
 import { isStripeSubscriptionTrialing } from "@/external/stripe/subscriptions/utils/classifyStripeSubscriptionUtils";
 import type { AutumnContext } from "@/honoUtils/HonoEnv";
 import { getLineItemBillingPeriod } from "@/internal/billing/v2/utils/lineItems/getLineItemBillingPeriod";
+import { getRefundLineItemForPrice } from "@/internal/billing/v2/utils/lineItems/getRefundLineItemForPrice";
 import type { AllocatedInvoiceContext } from "../allocatedInvoiceContext";
 import { allocatedInvoiceIsUpgrade } from "./allocatedInvoiceIsUpgrade";
 
@@ -66,7 +69,7 @@ export const computeAllocatedInvoiceLineItems = ({
 		customerProduct,
 	};
 
-	const previousLIneItem = usagePriceToLineItem({
+	const catalogRefundLineItem = usagePriceToLineItem({
 		cusEnt: previousCustomerEntitlement,
 		context: {
 			...lineItemContext,
@@ -78,6 +81,14 @@ export const computeAllocatedInvoiceLineItems = ({
 		},
 	});
 
+	const previousLineItem = getRefundLineItemForPrice({
+		ctx,
+		customerProduct,
+		billingContext,
+		priceId: customerPrice.price.id,
+		catalogFallback: catalogRefundLineItem,
+	});
+
 	const newLineItem = usagePriceToLineItem({
 		cusEnt: billingContext.updatedCustomerEntitlement,
 		context: lineItemContext,
@@ -87,15 +98,16 @@ export const computeAllocatedInvoiceLineItems = ({
 		},
 	});
 
-	// Don't return line items if they sum to 0
+	const netAmount = Math.abs(
-	if (
 		sumValues([
-			previousLIneItem?.amountAfterDiscounts ?? 0,
+			previousLineItem?.amountAfterDiscounts ?? 0,
 			newLineItem?.amountAfterDiscounts ?? 0,
-		]) === 0
+		]),
-	) {
+	);
-		return [];
-	}
 
-	return [previousLIneItem, newLineItem];
+	if (netAmount < BILLING_AMOUNT_EPSILON) return [];
+
+	return [previousLineItem, newLineItem].filter(
+		(li): li is LineItem => li !== undefined,
+	);
 };

server/src/internal/balances/utils/allocatedInvoice/setupAllocatedInvoiceContext.ts

@@ -10,6 +10,7 @@ import {
 } from "@autumn/shared";
 import type { AutumnContext } from "@/honoUtils/HonoEnv.js";
 import { setupStripeBillingContext } from "@/internal/billing/v2/providers/stripe/setup/setupStripeBillingContext.js";
+import { fetchStoredLineItemsForBilling } from "@/internal/billing/v2/setup/fetchStoredLineItemsForBilling.js";
 import { setupFullCustomerContext } from "@/internal/billing/v2/setup/setupFullCustomerContext.js";
 import { applyDeductionUpdateToCustomerEntitlement } from "../deduction/applyDeductionUpdateToCustomerEntitlement.js";
 import { applyDeductionUpdateToFullCustomer } from "../deduction/applyDeductionUpdateToFullCustomer.js";
@@ -108,6 +109,12 @@ export const setupAllocatedInvoiceContext = async ({
 		cusEnt: newCustomerEntitlement,
 	});
 
+	const { storedChargeLineItems, storedRefundLineItems } =
+		await fetchStoredLineItemsForBilling({
+			db: ctx.db,
+			customerProductIds: [cusProduct.id],
+		});
+
 	return {
 		// BillingContext fields
 		fullCustomer,
@@ -120,6 +127,8 @@ export const setupAllocatedInvoiceContext = async ({
 		stripeSubscription,
 		stripeSubscriptionSchedule,
 		stripeDiscounts,
+		storedChargeLineItems,
+		storedRefundLineItems,
 		paymentMethod,
 		billingVersion: BillingVersion.V2,
 

server/src/internal/billing/v2/actions/attach/setup/setupAttachBillingContext.ts

@@ -26,6 +26,7 @@ import { setupInvoiceModeContext } from "@/internal/billing/v2/setup/setupInvoic
 import { setupPaymentBehaviorIntent } from "@/internal/billing/v2/setup/setupPaymentBehaviorIntent";
 import { setupResetCycleAnchor } from "@/internal/billing/v2/setup/setupResetCycleAnchor";
 import { setupTransitionConfigs } from "@/internal/billing/v2/setup/setupTransitionConfigs";
+import { fetchStoredLineItemsForSubscriptionBilling } from "@/internal/billing/v2/setup/fetchStoredLineItemsForSubscriptionBilling";
 import { setupAdjustableQuantities } from "../../../setup/setupAdjustableQuantities";
 import { setupAnchorResetRefund } from "../../../setup/setupAnchorResetRefund";
 import { setupIgnoreProrationBehavior } from "../../../setup/setupIgnoreProrationBehavior";
@@ -261,6 +262,17 @@ export const setupAttachBillingContext = async ({
 		contextOverride,
 	});
 
+	const outgoingCusProductIds = currentCustomerProduct
+		? [currentCustomerProduct.id]
+		: [];
+	const { storedChargeLineItems, storedRefundLineItems } =
+		await fetchStoredLineItemsForSubscriptionBilling({
+			db: ctx.db,
+			fullCustomer,
+			stripeSubscription,
+			outgoingCusProductIds,
+		});
+
 	return {
 		fullCustomer,
 		fullProducts: [attachProduct],
@@ -321,6 +333,9 @@ export const setupAttachBillingContext = async ({
 		skipBillingChanges,
 		dryRunStripe: preview,
 
+		storedChargeLineItems,
+		storedRefundLineItems,
+
 		anchorResetRefund: setupAnchorResetRefund({
 			billingCycleAnchor: params.billing_cycle_anchor,
 			prorationBehavior: params.proration_behavior,

server/src/internal/billing/v2/actions/common/immediateMultiProduct/setupImmediateMultiProductBillingContext.ts

@@ -15,6 +15,7 @@ import { setupAttachProductContext } from "@/internal/billing/v2/actions/attach/
 import { setupAttachTransitionContext } from "@/internal/billing/v2/actions/attach/setup/setupAttachTransitionContext";
 import { setupStripeBillingContext } from "@/internal/billing/v2/providers/stripe/setup/setupStripeBillingContext";
 import { setupBillingCycleAnchor } from "@/internal/billing/v2/setup/setupBillingCycleAnchor";
+import { fetchStoredLineItemsForSubscriptionBilling } from "@/internal/billing/v2/setup/fetchStoredLineItemsForSubscriptionBilling";
 import { setupFeatureQuantitiesContext } from "@/internal/billing/v2/setup/setupFeatureQuantitiesContext";
 import { setupFullCustomerContext } from "@/internal/billing/v2/setup/setupFullCustomerContext";
 import { setupInvoiceModeContext } from "@/internal/billing/v2/setup/setupInvoiceModeContext";
@@ -226,6 +227,17 @@ export const setupImmediateMultiProductBillingContext = async ({
 		(productContext) => productContext.customEnts,
 	);
 
+	const outgoingCusProductIds = productContexts
+		.map((pc) => pc.currentCustomerProduct?.id)
+		.filter((id): id is string => id != null);
+	const { storedChargeLineItems, storedRefundLineItems } =
+		await fetchStoredLineItemsForSubscriptionBilling({
+			db: ctx.db,
+			fullCustomer,
+			stripeSubscription,
+			outgoingCusProductIds,
+		});
+
 	return {
 		fullCustomer,
 		fullProducts,
@@ -265,5 +277,7 @@ export const setupImmediateMultiProductBillingContext = async ({
 			params.success_url ?? orgToReturnUrl({ org: ctx.org, env: ctx.env }),
 		checkoutSessionParams: params.checkout_session_params,
 		dryRunStripe: preview,
+		storedChargeLineItems,
+		storedRefundLineItems,
 	};
 };

server/src/internal/billing/v2/actions/updateSubscription/compute/updateQuantity/computeUpdateQuantityLineItems.ts

@@ -1,5 +1,6 @@
 import type { BillingContext } from "@autumn/shared";
 import {
+	BILLING_AMOUNT_EPSILON,
 	type BillingPeriod,
 	cloneEntitlementWithUpdatedQuantity,
 	cusEntToCusPrice,
@@ -8,6 +9,7 @@ import {
 	type FullCusProduct,
 	findPrepaidCustomerEntitlement,
 	InternalError,
+	type LineItem,
 	type LineItemContext,
 	orgToCurrency,
 	priceToProrationConfig,
@@ -15,6 +17,7 @@ import {
 	usagePriceToLineItem,
 } from "@autumn/shared";
 import type { AutumnContext } from "@/honoUtils/HonoEnv";
+import { getRefundLineItemForPrice } from "@/internal/billing/v2/utils/lineItems/getRefundLineItemForPrice";
 
 export const computeUpdateQuantityLineItems = ({
 	ctx,
@@ -88,7 +91,7 @@ export const computeUpdateQuantityLineItems = ({
 		customerProduct,
 	};
 
-	const refundLineItem = usagePriceToLineItem({
+	const catalogRefundLineItem = usagePriceToLineItem({
 		cusEnt: prepaidCustomerEntitlement,
 		context: {
 			...lineItemContext,
@@ -100,6 +103,14 @@ export const computeUpdateQuantityLineItems = ({
 		},
 	});
 
+	const refundLineItem = getRefundLineItemForPrice({
+		ctx,
+		customerProduct,
+		billingContext,
+		priceId: customerPrice.price.id,
+		catalogFallback: catalogRefundLineItem,
+	});
+
 	const chargeLineItem = usagePriceToLineItem({
 		cusEnt: newCustomerEntitlement,
 		context: lineItemContext,
@@ -109,15 +120,16 @@ export const computeUpdateQuantityLineItems = ({
 		},
 	});
 
-	// Don't return line items if they sum to 0
+	const netAmount = Math.abs(
-	if (
 		sumValues([
 			refundLineItem?.amountAfterDiscounts ?? 0,
 			chargeLineItem?.amountAfterDiscounts ?? 0,
-		]) === 0
+		]),
-	) {
+	);
-		return [];
-	}
 
-	return [refundLineItem, chargeLineItem];
+	if (netAmount < BILLING_AMOUNT_EPSILON) return [];
+
+	return [refundLineItem, chargeLineItem].filter(
+		(li): li is LineItem => li !== undefined,
+	);
 };

server/src/internal/billing/v2/actions/updateSubscription/setup/setupUpdateSubscriptionBillingContext.ts

@@ -19,6 +19,7 @@ import { setupFullCustomerContext } from "@/internal/billing/v2/setup/setupFullC
 import { setupIgnoreProrationBehavior } from "@/internal/billing/v2/setup/setupIgnoreProrationBehavior";
 import { setupInvoiceModeContext } from "@/internal/billing/v2/setup/setupInvoiceModeContext";
 import { setupResetCycleAnchor } from "@/internal/billing/v2/setup/setupResetCycleAnchor";
+import { fetchStoredLineItemsForSubscriptionBilling } from "@/internal/billing/v2/setup/fetchStoredLineItemsForSubscriptionBilling";
 import { setupAttachCheckoutMode } from "../../attach/setup/setupAttachCheckoutMode";
 import { setupUpdateSubscriptionIntent } from "./setupUpdateSubscriptionIntent";
 import { setupUpdateSubscriptionTrialContext } from "./setupUpdateSubscriptionTrialContext";
@@ -176,6 +177,14 @@ export const setupUpdateSubscriptionBillingContext = async ({
 		customerProduct,
 	});
 
+	const { storedChargeLineItems, storedRefundLineItems } =
+		await fetchStoredLineItemsForSubscriptionBilling({
+			db: ctx.db,
+			fullCustomer,
+			stripeSubscription,
+			outgoingCusProductIds: [customerProduct.id],
+		});
+
 	return {
 		intent,
 		fullCustomer,
@@ -217,6 +226,9 @@ export const setupUpdateSubscriptionBillingContext = async ({
 		skipBillingChanges,
 		dryRunStripe: preview,
 
+		storedChargeLineItems,
+		storedRefundLineItems,
+
 		checkoutMode,
 
 		anchorResetRefund: setupAnchorResetRefund({

server/src/internal/billing/v2/compute/computeAutumnUtils/buildAutumnLineItems.ts

@@ -5,6 +5,7 @@ import type {
 	UpdateCustomerEntitlement,
 } from "@autumn/shared";
 import { customerProductToArrearLineItems } from "@/internal/billing/v2/utils/lineItems/customerProductToArrearLineItems";
+import { getRefundLineItems } from "@/internal/billing/v2/utils/lineItems/getRefundLineItems";
 import type { AutumnContext } from "../../../../../honoUtils/HonoEnv";
 import { customerProductToLineItems } from "../../utils/lineItems/customerProductToLineItems";
 import { logBuildAutumnLineItems } from "./logBuildAutumnLineItems";
@@ -55,11 +56,10 @@ export const buildAutumnLineItems = ({
 
 	// Get line items for ongoing cus product
 	const deletedLineItems = customerProductsToDelete.flatMap((customerProduct) =>
-		customerProductToLineItems({
+		getRefundLineItems({
 			ctx,
 			customerProduct,
 			billingContext,
-			direction: "refund",
 			priceFilters: { excludeOneOffPrices: true },
 		}),
 	);

server/src/internal/billing/v2/compute/computeAutumnUtils/buildSharedSubscriptionTrialLineItems.ts

@@ -13,7 +13,7 @@ import {
 	getDeleteCustomerProducts,
 	getUpdateCustomerProducts,
 } from "@/internal/billing/v2/utils/billingPlan/customerProductPlanMutations";
-import { customerProductToLineItems } from "@/internal/billing/v2/utils/lineItems/customerProductToLineItems";
+import { getLineItemsForDirection } from "@/internal/billing/v2/utils/lineItems/getLineItemsForDirection";
 
 const formatLineItem = (item: LineItem) => ({
 	description: item.description,
@@ -141,9 +141,9 @@ export const buildSharedSubscriptionTrialLineItems = ({
 	const lineItems: LineItem[] = [];
 	for (const customerProduct of siblingCustomerProducts) {
 		lineItems.push(
-			...customerProductToLineItems({
+			...getLineItemsForDirection({
 				ctx,
-				customerProduct: customerProduct,
+				customerProduct,
 				billingContext,
 				direction,
 				priceFilters: { excludeOneOffPrices: true },

server/src/internal/billing/v2/setup/fetchStoredLineItemsForBilling.ts

@@ -0,0 +1,53 @@
+import type { DbInvoiceLineItem } from "@autumn/shared";
+import type { DrizzleCli } from "@/db/initDrizzle";
+import { invoiceLineItemRepo } from "@/internal/invoices/lineItems/repos";
+
+const deduplicateById = (rows: DbInvoiceLineItem[]): DbInvoiceLineItem[] => {
+	const seen = new Set<string>();
+	return rows.filter((row) => {
+		if (seen.has(row.id)) return false;
+		seen.add(row.id);
+		return true;
+	});
+};
+
+export const fetchStoredLineItemsForBilling = async ({
+	db,
+	customerProductIds,
+}: {
+	db: DrizzleCli;
+	customerProductIds: string[];
+}): Promise<{
+	storedChargeLineItems: DbInvoiceLineItem[];
+	storedRefundLineItems: DbInvoiceLineItem[];
+}> => {
+	if (customerProductIds.length === 0) {
+		return { storedChargeLineItems: [], storedRefundLineItems: [] };
+	}
+
+	const [chargeResults, refundResults] = await Promise.all([
+		Promise.all(
+			customerProductIds.map((cusProductId) =>
+				invoiceLineItemRepo.getByCustomerProductAndPeriod({
+					db,
+					customerProductId: cusProductId,
+					direction: "charge",
+				}),
+			),
+		),
+		Promise.all(
+			customerProductIds.map((cusProductId) =>
+				invoiceLineItemRepo.getByCustomerProductAndPeriod({
+					db,
+					customerProductId: cusProductId,
+					direction: "refund",
+				}),
+			),
+		),
+	]);
+
+	return {
+		storedChargeLineItems: deduplicateById(chargeResults.flat()),
+		storedRefundLineItems: deduplicateById(refundResults.flat()),
+	};
+};

server/src/internal/billing/v2/setup/fetchStoredLineItemsForSubscriptionBilling.ts

@@ -0,0 +1,27 @@
+import type { FullCustomer } from "@autumn/shared";
+import type Stripe from "stripe";
+import type { DrizzleCli } from "@/db/initDrizzle";
+import { fetchStoredLineItemsForBilling } from "./fetchStoredLineItemsForBilling";
+import { getSiblingCusProductIds } from "./getSiblingCusProductIds";
+
+export const fetchStoredLineItemsForSubscriptionBilling = async ({
+	db,
+	fullCustomer,
+	stripeSubscription,
+	outgoingCusProductIds,
+}: {
+	db: DrizzleCli;
+	fullCustomer: FullCustomer;
+	stripeSubscription?: Stripe.Subscription;
+	outgoingCusProductIds: string[];
+}) => {
+	const siblingIds = getSiblingCusProductIds({
+		fullCustomer,
+		stripeSubscription,
+		excludeIds: outgoingCusProductIds,
+	});
+	return fetchStoredLineItemsForBilling({
+		db,
+		customerProductIds: [...outgoingCusProductIds, ...siblingIds],
+	});
+};

server/src/internal/billing/v2/setup/getSiblingCusProductIds.ts

@@ -0,0 +1,26 @@
+import { cp, type FullCustomer } from "@autumn/shared";
+import type Stripe from "stripe";
+
+export const getSiblingCusProductIds = ({
+	fullCustomer,
+	stripeSubscription,
+	excludeIds = [],
+}: {
+	fullCustomer: FullCustomer;
+	stripeSubscription?: Stripe.Subscription;
+	excludeIds?: string[];
+}): string[] => {
+	if (!stripeSubscription) return [];
+
+	const excluded = new Set(excludeIds);
+
+	return fullCustomer.customer_products
+		.filter(
+			(cusProduct) =>
+				!excluded.has(cusProduct.id) &&
+				cp(cusProduct).paid().recurring().onStripeSubscription({
+					stripeSubscriptionId: stripeSubscription.id,
+				}).valid,
+		)
+		.map((cusProduct) => cusProduct.id);
+};

server/src/internal/billing/v2/utils/billingPlan/toNextCyclePreview/billingPlanToNextCycleLineItems.ts

@@ -11,7 +11,7 @@ import type { AutumnContext } from "@/honoUtils/HonoEnv";
 import { applyStripeDiscountsToLineItems } from "@/internal/billing/v2/providers/stripe/utils/discounts/applyStripeDiscountsToLineItems";
 import { filterStripeDiscountsForNextCycle } from "@/internal/billing/v2/providers/stripe/utils/discounts/filterStripeDiscountsForNextCycle";
 import { customerProductToArrearLineItems } from "../../lineItems/customerProductToArrearLineItems";
-import { customerProductToLineItems } from "../../lineItems/customerProductToLineItems";
+import { getLineItemsForDirection } from "../../lineItems/getLineItemsForDirection";
 import { lineItemToPreviewLineItem } from "../../lineItems/lineItemToPreviewLineItem";
 import { lineItemToPreviewUsageLineItem } from "../../lineItems/lineItemToPreviewUsageLineItem";
 
@@ -38,7 +38,7 @@ const buildLineItemsForSpec = ({
 	nextCycleStart: number;
 }) => {
 	const lineItems = spec.customerProducts.flatMap((customerProduct) =>
-		customerProductToLineItems({
+		getLineItemsForDirection({
 			ctx,
 			customerProduct,
 			billingContext: {

server/src/internal/billing/v2/utils/lineItems/chargeRowToRefundLineItem.ts

@@ -0,0 +1,95 @@
+import { generateKsuid } from "@autumn/ksuid";
+import type { BillingContext } from "@autumn/shared";
+import {
+	customerProductToEntity,
+	type DbInvoiceLineItem,
+	type FullCusProduct,
+	type InvoiceLineItemDiscount,
+	type LineItem,
+	type LineItemContext,
+	LineItemSchema,
+	orgToCurrency,
+} from "@autumn/shared";
+import type { AutumnContext } from "@/honoUtils/HonoEnv";
+
+export const chargeRowToRefundLineItem = ({
+	chargeRow,
+	creditAmount,
+	customerProduct,
+	billingContext,
+	ctx,
+}: {
+	chargeRow: DbInvoiceLineItem;
+	creditAmount: number;
+	customerProduct: FullCusProduct;
+	billingContext: BillingContext;
+	ctx: AutumnContext;
+}): LineItem => {
+	const periodStart =
+		chargeRow.effective_period_start ?? billingContext.currentEpochMs;
+	const periodEnd =
+		chargeRow.effective_period_end ?? billingContext.currentEpochMs;
+
+	const entity = customerProductToEntity({
+		customerProduct,
+		entities: billingContext.fullCustomer.entities,
+	});
+
+	const matchingCusPrice = customerProduct.customer_prices.find(
+		(cp) => cp.price.id === chargeRow.price_id,
+	);
+	const price =
+		matchingCusPrice?.price ?? customerProduct.customer_prices[0]?.price;
+
+	if (!price) {
+		throw new Error(
+			`[chargeRowToRefundLineItem] No price found on cusProduct ${customerProduct.id} for charge row ${chargeRow.id}`,
+		);
+	}
+
+	const context: LineItemContext = {
+		price,
+		product: customerProduct.product,
+		feature: undefined,
+		currency: orgToCurrency({ org: ctx.org }),
+		billingPeriod: { start: periodStart, end: periodEnd },
+		effectivePeriod: { start: billingContext.currentEpochMs, end: periodEnd },
+		direction: "refund",
+		now: billingContext.currentEpochMs,
+		billingTiming: "in_advance",
+		discountable: false,
+		entity,
+		customerProduct,
+		customerPrice: matchingCusPrice,
+	};
+
+	const description = chargeRow.description
+		? `Unused ${chargeRow.description}`
+		: `Unused ${customerProduct.product.name}`;
+
+	const lineItemData = {
+		id: generateKsuid({ prefix: "invoice_li_" }),
+		amount: creditAmount,
+		amountAfterDiscounts: creditAmount,
+		description,
+		context,
+		stripePriceId: chargeRow.stripe_price_id ?? undefined,
+		stripeProductId: chargeRow.stripe_product_id ?? undefined,
+		chargeImmediately: true,
+		prorated: true,
+		discounts:
+			(chargeRow.discounts as InvoiceLineItemDiscount[] | null)?.map((d) => ({
+				amountOff: d.amount_off,
+				percentOff: d.percent_off,
+				stripeCouponId: d.stripe_coupon_id,
+				couponName: d.stripe_coupon_id,
+			})) ?? [],
+	};
+
+	const result = LineItemSchema.safeParse(lineItemData);
+	if (!result.success) {
+		throw result.error;
+	}
+
+	return result.data;
+};

server/src/internal/billing/v2/utils/lineItems/getLineItemsForDirection.ts

@@ -0,0 +1,39 @@
+import type { BillingContext, FullCusProduct, LineItem } from "@autumn/shared";
+import type { AutumnContext } from "@/honoUtils/HonoEnv";
+import { customerProductToLineItems } from "./customerProductToLineItems";
+import { getRefundLineItems } from "./getRefundLineItems";
+
+export const getLineItemsForDirection = ({
+	ctx,
+	customerProduct,
+	billingContext,
+	direction,
+	priceFilters,
+	billingCycleAnchorMsOverride,
+}: {
+	ctx: AutumnContext;
+	customerProduct: FullCusProduct;
+	billingContext: BillingContext;
+	direction: "charge" | "refund";
+	priceFilters?: { excludeOneOffPrices?: boolean };
+	billingCycleAnchorMsOverride?: BillingContext["billingCycleAnchorMs"];
+}): LineItem[] => {
+	if (direction === "refund") {
+		return getRefundLineItems({
+			ctx,
+			customerProduct,
+			billingContext,
+			priceFilters,
+			billingCycleAnchorMsOverride,
+		});
+	}
+
+	return customerProductToLineItems({
+		ctx,
+		customerProduct,
+		billingContext,
+		direction,
+		priceFilters,
+		billingCycleAnchorMsOverride,
+	});
+};

server/src/internal/billing/v2/utils/lineItems/getRefundLineItemForPrice.ts

@@ -0,0 +1,29 @@
+import type { BillingContext, FullCusProduct, LineItem } from "@autumn/shared";
+import type { AutumnContext } from "@/honoUtils/HonoEnv";
+import { getRefundLineItems } from "./getRefundLineItems";
+
+export const getRefundLineItemForPrice = ({
+	ctx,
+	customerProduct,
+	billingContext,
+	priceId,
+	catalogFallback,
+}: {
+	ctx: AutumnContext;
+	customerProduct: FullCusProduct;
+	billingContext: BillingContext;
+	priceId: string;
+	catalogFallback: LineItem | undefined;
+}): LineItem | undefined => {
+	const matchedRefundLineItems = getRefundLineItems({
+		ctx,
+		customerProduct,
+		billingContext,
+	});
+
+	const matchedRefundForPrice = matchedRefundLineItems.find(
+		(li) => li.context.price.id === priceId,
+	);
+
+	return matchedRefundForPrice ?? catalogFallback;
+};

server/src/internal/billing/v2/utils/lineItems/getRefundLineItems.ts

@@ -0,0 +1,38 @@
+import type { BillingContext, FullCusProduct, LineItem } from "@autumn/shared";
+import type { AutumnContext } from "@/honoUtils/HonoEnv";
+import { customerProductToLineItems } from "./customerProductToLineItems";
+import { invoiceCreditFromStoredLineItems } from "./invoiceCreditFromStoredLineItems";
+
+export const getRefundLineItems = ({
+	ctx,
+	customerProduct,
+	billingContext,
+	priceFilters,
+	billingCycleAnchorMsOverride,
+}: {
+	ctx: AutumnContext;
+	customerProduct: FullCusProduct;
+	billingContext: BillingContext;
+	priceFilters?: { excludeOneOffPrices?: boolean };
+	billingCycleAnchorMsOverride?: BillingContext["billingCycleAnchorMs"];
+}): LineItem[] => {
+	const { lineItems: matchedCredits, allPricesResolved } =
+		invoiceCreditFromStoredLineItems({
+			ctx,
+			customerProduct,
+			billingContext,
+		});
+
+	if (allPricesResolved) return matchedCredits;
+
+	const catalogCredits = customerProductToLineItems({
+		ctx,
+		customerProduct,
+		billingContext,
+		direction: "refund",
+		priceFilters,
+		billingCycleAnchorMsOverride,
+	});
+
+	return [...matchedCredits, ...catalogCredits];
+};

server/src/internal/billing/v2/utils/lineItems/invoiceCreditFromStoredLineItems.ts

@@ -0,0 +1,120 @@
+import type { BillingContext } from "@autumn/shared";
+import {
+	type FullCusProduct,
+	isOneOffPrice,
+	type LineItem,
+} from "@autumn/shared";
+import type { AutumnContext } from "@/honoUtils/HonoEnv";
+import { chargeRowToRefundLineItem } from "./chargeRowToRefundLineItem";
+import {
+	computeAlreadyRefundedForCharge,
+	computeProratedCredit,
+	splitMultiEntityAmount,
+} from "./storedLineItemUtils";
+
+type InvoiceMatchedCreditResult = {
+	lineItems: LineItem[];
+	allPricesResolved: boolean;
+};
+
+export const invoiceCreditFromStoredLineItems = ({
+	ctx,
+	customerProduct,
+	billingContext,
+}: {
+	ctx: AutumnContext;
+	customerProduct: FullCusProduct;
+	billingContext: BillingContext;
+}): InvoiceMatchedCreditResult => {
+	const { logger } = ctx;
+	const now = billingContext.currentEpochMs;
+	const chargeRows = billingContext.storedChargeLineItems ?? [];
+	const refundRows = billingContext.storedRefundLineItems ?? [];
+
+	const pricesToCredit = customerProduct.customer_prices.filter(
+		(cp) => !isOneOffPrice(cp.price),
+	);
+
+	if (pricesToCredit.length === 0) {
+		return { lineItems: [], allPricesResolved: true };
+	}
+
+	const allLineItems: LineItem[] = [];
+	let anyMissed = false;
+
+	for (const cusPrice of pricesToCredit) {
+		const priceChargeRows = chargeRows.filter(
+			(row) =>
+				row.customer_product_ids.includes(customerProduct.id) &&
+				(row.price_id === cusPrice.price.id ||
+					row.stripe_price_id === cusPrice.price.config?.stripe_price_id),
+		);
+
+		const usableRows = priceChargeRows.filter(
+			(row) =>
+				row.customer_product_ids.length > 0 &&
+				row.effective_period_start != null &&
+				row.effective_period_end != null &&
+				row.effective_period_start < now &&
+				row.effective_period_end > now,
+		);
+
+		if (usableRows.length === 0) {
+			anyMissed = true;
+			logger.warn(
+				`[invoiceCreditFromStoredLineItems] No usable stored charge row for cusProduct=${customerProduct.id} price=${cusPrice.price.id}; falling back to catalog synthesis`,
+			);
+			continue;
+		}
+
+		const currentPeriodRefunds = refundRows.filter(
+			(r) =>
+				r.customer_product_ids.includes(customerProduct.id) &&
+				r.effective_period_end != null &&
+				r.effective_period_start != null &&
+				r.effective_period_start < now &&
+				r.effective_period_end > now,
+		);
+
+		for (const chargeRow of usableRows) {
+			const attributedAmount = splitMultiEntityAmount(chargeRow);
+
+			const alreadyRefunded = computeAlreadyRefundedForCharge({
+				chargeRow,
+				refundRows: currentPeriodRefunds,
+			});
+
+			const adjustedChargeRow = {
+				...chargeRow,
+				amount_after_discounts: attributedAmount,
+			};
+
+			const creditAmount = computeProratedCredit({
+				chargeRow: adjustedChargeRow,
+				now,
+				alreadyRefunded,
+			});
+
+			if (creditAmount === 0) continue;
+
+			allLineItems.push(
+				chargeRowToRefundLineItem({
+					chargeRow,
+					creditAmount,
+					customerProduct,
+					billingContext,
+					ctx,
+				}),
+			);
+		}
+	}
+
+	if (anyMissed && allLineItems.length === 0) {
+		return { lineItems: [], allPricesResolved: false };
+	}
+
+	return {
+		lineItems: allLineItems,
+		allPricesResolved: !anyMissed,
+	};
+};

server/src/internal/billing/v2/utils/lineItems/storedLineItemUtils.ts

@@ -0,0 +1,81 @@
+import type { DbInvoiceLineItem } from "@autumn/shared";
+import { Decimal } from "decimal.js";
+
+export const isWithinPeriod = (
+	inner: DbInvoiceLineItem,
+	outer: DbInvoiceLineItem,
+): boolean =>
+	inner.effective_period_start != null &&
+	outer.effective_period_start != null &&
+	inner.effective_period_end != null &&
+	outer.effective_period_end != null &&
+	inner.effective_period_start >= outer.effective_period_start &&
+	inner.effective_period_end <= outer.effective_period_end;
+
+export const hasSamePrice = (
+	a: DbInvoiceLineItem,
+	b: DbInvoiceLineItem,
+): boolean =>
+	(a.price_id != null && a.price_id === b.price_id) ||
+	(a.stripe_price_id != null && a.stripe_price_id === b.stripe_price_id);
+
+export const computeProratedCredit = ({
+	chargeRow,
+	now,
+	alreadyRefunded,
+}: {
+	chargeRow: DbInvoiceLineItem;
+	now: number;
+	alreadyRefunded: number;
+}): number => {
+	const periodStart = chargeRow.effective_period_start;
+	const periodEnd = chargeRow.effective_period_end;
+
+	if (periodStart == null || periodEnd == null || periodEnd <= periodStart) {
+		return 0;
+	}
+
+	const totalCharged = chargeRow.amount_after_discounts;
+	const refundable = new Decimal(totalCharged).minus(alreadyRefunded);
+
+	if (refundable.lte(0)) return 0;
+
+	const remaining = new Decimal(periodEnd).minus(now);
+	const total = new Decimal(periodEnd).minus(periodStart);
+
+	if (remaining.lte(0)) return 0;
+
+	const prorationFraction = remaining.div(total);
+	return prorationFraction.mul(refundable).neg().toNumber();
+};
+
+export const computeAlreadyRefundedForCharge = ({
+	chargeRow,
+	refundRows,
+}: {
+	chargeRow: DbInvoiceLineItem;
+	refundRows: DbInvoiceLineItem[];
+}): number => {
+	const matchingRefunds = refundRows.filter(
+		(refund) =>
+			isWithinPeriod(refund, chargeRow) && hasSamePrice(refund, chargeRow),
+	);
+
+	return matchingRefunds.reduce(
+		(sum, r) =>
+			new Decimal(sum)
+				.plus(Math.abs(splitMultiEntityAmount(r)))
+				.toNumber(),
+		0,
+	);
+};
+
+export const splitMultiEntityAmount = (
+	chargeRow: DbInvoiceLineItem,
+): number => {
+	const ids = chargeRow.customer_product_ids;
+	if (ids.length <= 1) return chargeRow.amount_after_discounts;
+	return new Decimal(chargeRow.amount_after_discounts)
+		.div(ids.length)
+		.toNumber();
+};

server/src/internal/invoices/lineItems/repos/getByCustomerProductAndPeriod.ts

@@ -0,0 +1,43 @@
+import { type DbInvoiceLineItem, invoiceLineItems } from "@autumn/shared";
+import { and, eq, gte, lte, sql } from "drizzle-orm";
+import type { DrizzleCli } from "@/db/initDrizzle";
+
+export const getByCustomerProductAndPeriod = async ({
+	db,
+	customerProductId,
+	direction,
+	priceId,
+	periodStartMs,
+	periodEndMs,
+}: {
+	db: DrizzleCli;
+	customerProductId: string;
+	direction: "charge" | "refund";
+	priceId?: string;
+	periodStartMs?: number;
+	periodEndMs?: number;
+}): Promise<DbInvoiceLineItem[]> => {
+	const conditions = [
+		eq(invoiceLineItems.direction, direction),
+		sql`${invoiceLineItems.customer_product_ids}::jsonb @> ${JSON.stringify([customerProductId])}::jsonb`,
+	];
+
+	if (priceId) {
+		conditions.push(eq(invoiceLineItems.price_id, priceId));
+	}
+
+	if (periodStartMs !== undefined) {
+		conditions.push(
+			lte(invoiceLineItems.effective_period_start, periodStartMs),
+		);
+	}
+
+	if (periodEndMs !== undefined) {
+		conditions.push(gte(invoiceLineItems.effective_period_end, periodEndMs));
+	}
+
+	return db
+		.select()
+		.from(invoiceLineItems)
+		.where(and(...conditions));
+};

server/src/internal/invoices/lineItems/repos/index.ts

@@ -1,5 +1,6 @@
 import { deleteByInvoiceId } from "./deleteByInvoiceId";
 import { deleteStaleByStripeInvoiceId } from "./deleteStaleByStripeInvoiceId";
+import { getByCustomerProductAndPeriod } from "./getByCustomerProductAndPeriod";
 import { getByInvoiceId } from "./getByInvoiceId";
 import { getByInvoiceIds } from "./getByInvoiceIds";
 import { getByStripeInvoiceId } from "./getByStripeInvoiceId";
@@ -18,6 +19,7 @@ export const invoiceLineItemRepo = {
 	getByInvoiceId,
 	getByInvoiceIds,
 	getByStripeInvoiceId,
+	getByCustomerProductAndPeriod,
 	deleteByInvoiceId,
 	deleteStaleByStripeInvoiceId,
 	getDeferredByInvoiceItemIds,

server/tests/integration/billing/invoice-matched-credits/additional-coverage.test.ts

@@ -0,0 +1,290 @@
+/**
+ * Invoice-Matched Proration Credits — Additional Coverage
+ *
+ * 1. amount-off coupon cancel: refund based on discounted invoice
+ * 2. cancel after partial refund (upgrade then cancel): second refund nets the first
+ * 3. create-schedule with discount: immediate phase credit from stored charge
+ */
+
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3, AttachPreviewResponse } from "@autumn/shared";
+import { expectCustomerInvoiceCorrect } from "@tests/integration/billing/utils/expectCustomerInvoiceCorrect";
+import {
+	expectProductActive,
+	expectProductNotPresent,
+} from "@tests/integration/billing/utils/expectCustomerProductCorrect";
+import { items } from "@tests/utils/fixtures/items";
+import { products } from "@tests/utils/fixtures/products";
+import { advanceTestClock } from "@tests/utils/stripeUtils";
+import { advanceToNextInvoice } from "@tests/utils/testAttachUtils/testAttachUtils";
+import ctx from "@tests/utils/testInitUtils/createTestContext";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario";
+import chalk from "chalk";
+import { createStripeCli } from "@/external/connect/createStripeCli";
+import { createAmountCoupon } from "../utils/discounts/discountTestUtils";
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 1: Amount-off coupon cancel — refund based on discounted invoice ($15)
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits additional 1: amount-off coupon cancel — refund based on discounted invoice")}`,
+	async () => {
+		const customerId = "imc-add-amtoff-cancel";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, testClockId, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [pro] }),
+			],
+			actions: [],
+		});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createAmountCoupon({
+			stripeCli,
+			amountOffCents: 500,
+		});
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: pro.id,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customerAfterAttach =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterAttach,
+			count: 1,
+			latestTotal: 15,
+		});
+
+		const renewedAt = await advanceToNextInvoice({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			currentEpochMs: advancedTo,
+		});
+
+		const customerAfterRenewal =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterRenewal,
+			count: 2,
+			latestTotal: 15,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewedAt),
+			numberOfDays: 15,
+		});
+
+		const cancelParams = {
+			customer_id: customerId,
+			product_id: pro.id,
+			cancel_action: "cancel_immediately" as const,
+		};
+
+		const preview = await autumnV1.subscriptions.previewUpdate(cancelParams);
+
+		expect(preview.total).toBeLessThan(0);
+		expect(Math.abs(preview.total)).toBeLessThan(10);
+		expect(Math.abs(preview.total)).toBeGreaterThan(5);
+
+		await autumnV1.subscriptions.update(cancelParams);
+
+		const customerAfterCancel =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductNotPresent({
+			customer: customerAfterCancel,
+			productId: pro.id,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterCancel,
+			count: 3,
+			latestTotal: preview.total,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 2: Cancel after partial refund (upgrade then cancel) — second refund nets the first
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits additional 2: cancel after upgrade — second refund nets the first")}`,
+	async () => {
+		const customerId = "imc-add-upg-then-cancel";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+				],
+				actions: [
+					s.billing.attach({ productId: pro.id }),
+					s.advanceTestClock({ toNextInvoice: true }),
+					s.advanceTestClock({ days: 10 }),
+				],
+			});
+
+		const upgradeResult = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(upgradeResult.invoice).toBeDefined();
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customerAfterUpgrade =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductActive({
+			customer: customerAfterUpgrade,
+			productId: `premium_${customerId}`,
+		});
+
+		const cancelParams = {
+			customer_id: customerId,
+			product_id: `premium_${customerId}`,
+			cancel_action: "cancel_immediately" as const,
+		};
+
+		const preview = await autumnV1.subscriptions.previewUpdate(cancelParams);
+
+		expect(preview.total).toBeLessThan(0);
+
+		await autumnV1.subscriptions.update(cancelParams);
+
+		const customerAfterCancel =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductNotPresent({
+			customer: customerAfterCancel,
+			productId: `premium_${customerId}`,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 3: Scheduled upgrade with discount — immediate phase credit from stored charge
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits additional 3: scheduled upgrade with discount — credit reflects discounted charge")}`,
+	async () => {
+		const customerId = "imc-add-sched-disc";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createAmountCoupon({
+			stripeCli,
+			amountOffCents: 400,
+		});
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customerAfterAttach =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterAttach,
+			count: 1,
+			latestTotal: 16,
+		});
+
+		const renewedAt = await advanceToNextInvoice({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			currentEpochMs: advancedTo,
+		});
+
+		const customerAfterRenewal =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterRenewal,
+			count: 2,
+			latestTotal: 16,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewedAt),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-16);
+
+		for (const creditLine of creditLines) {
+			const discounts = creditLine.discounts ?? [];
+			expect(discounts.length).toBe(0);
+		}
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(result.invoice?.total).toBeCloseTo(preview.total, 0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/cancel.test.ts

@@ -0,0 +1,279 @@
+/**
+ * Invoice-Matched Proration Credits — Cancel Tests
+ *
+ * Verifies that cancellation credits and refunds source amounts from stored
+ * invoice line items rather than catalog prices.
+ *
+ * - cancel_immediately with discount: credit reflects discounted charge ($16)
+ * - cancel_end_of_cycle: no immediate credit line items
+ * - refund_last_payment prorated with discount: refund based on discounted invoice
+ */
+
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3 } from "@autumn/shared";
+import { expectCustomerInvoiceCorrect } from "@tests/integration/billing/utils/expectCustomerInvoiceCorrect";
+import {
+	expectProductActive,
+	expectProductNotPresent,
+} from "@tests/integration/billing/utils/expectCustomerProductCorrect";
+import { items } from "@tests/utils/fixtures/items";
+import { products } from "@tests/utils/fixtures/products";
+import { advanceTestClock } from "@tests/utils/stripeUtils";
+import { advanceToNextInvoice } from "@tests/utils/testAttachUtils/testAttachUtils";
+import ctx from "@tests/utils/testInitUtils/createTestContext";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario";
+import chalk from "chalk";
+import { createStripeCli } from "@/external/connect/createStripeCli";
+import { createPercentCoupon } from "../utils/discounts/discountTestUtils";
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 1: Cancel immediately prorated with discount — credit from stored charge
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits cancel 1: cancel immediately with discount — credit reflects stored charge")}`,
+	async () => {
+		const customerId = "imc-cancel-imm-disc";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ paymentMethod: "success" }),
+					s.products({ list: [pro] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({
+			stripeCli,
+			percentOff: 20,
+		});
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: pro.id,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customerAfterAttach =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterAttach,
+			count: 1,
+			latestTotal: 16,
+		});
+
+		const renewedAt = await advanceToNextInvoice({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			currentEpochMs: advancedTo,
+		});
+
+		const customerAfterRenewal =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterRenewal,
+			count: 2,
+			latestTotal: 16,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewedAt),
+			numberOfDays: 15,
+		});
+
+		const cancelParams = {
+			customer_id: customerId,
+			product_id: pro.id,
+			cancel_action: "cancel_immediately" as const,
+		};
+
+		const preview = await autumnV1.subscriptions.previewUpdate(cancelParams);
+
+		expect(preview.total).toBeLessThan(0);
+		expect(preview.total).toBeGreaterThan(-16);
+		expect(preview.total).toBeLessThanOrEqual(-7);
+
+		await autumnV1.subscriptions.update(cancelParams);
+
+		const customerAfterCancel =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductNotPresent({
+			customer: customerAfterCancel,
+			productId: pro.id,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterCancel,
+			count: 3,
+			latestTotal: preview.total,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 2: Cancel end_of_cycle — no immediate credit lines
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits cancel 2: cancel end_of_cycle — no immediate credit line items")}`,
+	async () => {
+		const customerId = "imc-cancel-eoc";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, autumnV2_2 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [pro] }),
+			],
+			actions: [
+				s.billing.attach({ productId: pro.id }),
+				s.advanceTestClock({ days: 10 }),
+			],
+		});
+
+		const customerBeforeCancel =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductActive({
+			customer: customerBeforeCancel,
+			productId: pro.id,
+		});
+
+		const cancelParams = {
+			customer_id: customerId,
+			product_id: pro.id,
+			cancel_action: "cancel_end_of_cycle" as const,
+		};
+
+		const preview = await autumnV1.subscriptions.previewUpdate(cancelParams);
+
+		expect(preview.total).toBe(0);
+
+		const creditLines = preview.line_items.filter((li: { total: number }) => li.total < 0);
+		expect(creditLines.length).toBe(0);
+
+		await autumnV1.subscriptions.update(cancelParams);
+
+		const customerAfterCancel =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterCancel,
+			count: 1,
+			latestTotal: 20,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 3: Cancel discounted plan refund_last_payment prorated — refund based on discounted invoice
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits cancel 3: cancel with refund_last_payment prorated — refund reflects discounted invoice")}`,
+	async () => {
+		const customerId = "imc-cancel-refund-disc";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ paymentMethod: "success" }),
+					s.products({ list: [pro] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({
+			stripeCli,
+			percentOff: 20,
+		});
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: pro.id,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customerAfterAttach =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterAttach,
+			count: 1,
+			latestTotal: 16,
+		});
+
+		const renewedAt = await advanceToNextInvoice({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			currentEpochMs: advancedTo,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewedAt),
+			numberOfDays: 15,
+		});
+
+		const cancelParams = {
+			customer_id: customerId,
+			product_id: pro.id,
+			cancel_action: "cancel_immediately" as const,
+			refund_last_payment: "prorated" as const,
+		};
+
+		const preview = await autumnV1.subscriptions.previewUpdate(cancelParams);
+
+		expect(preview.total).toBe(0);
+		expect(preview.refund).toBeDefined();
+
+		const refundAmount = preview.refund!.amount;
+		expect(refundAmount).toBeGreaterThan(0);
+		expect(refundAmount).toBeLessThanOrEqual(16);
+		expect(refundAmount).toBeGreaterThanOrEqual(7);
+
+		expect(preview.refund!.invoice.total).toBe(16);
+
+		await autumnV1.subscriptions.update(cancelParams);
+
+		const customerAfterCancel =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductNotPresent({
+			customer: customerAfterCancel,
+			productId: pro.id,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterCancel,
+			count: 2,
+		});
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/create-schedule.test.ts

@@ -0,0 +1,99 @@
+import { expect, test } from "bun:test";
+import type { AttachPreviewResponse } from "@autumn/shared";
+import { hoursToFinalizeInvoice } from "@tests/utils/constants.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { advanceTestClock } from "@tests/utils/stripeUtils.js";
+import ctx from "@tests/utils/testInitUtils/createTestContext.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+import { addHours, addMonths } from "date-fns";
+import { createStripeCli } from "@/external/connect/createStripeCli.js";
+import { createPercentCoupon } from "../utils/discounts/discountTestUtils.js";
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits create-schedule: pro + addon credits reflect stored discounted charges")}`,
+	async () => {
+		const customerId = "imc-sched-disc-addon";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const addon = products.recurringAddOn({
+			id: "addon",
+			items: [items.monthlyWords({ includedUsage: 200 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, addon, premium] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `addon_${customerId}`,
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(Math.abs(creditTotal)).toBeLessThan(20 + 10);
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(result.invoice?.total).toBeCloseTo(preview.total, 0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/discount-coverage.test.ts

@@ -0,0 +1,282 @@
+import { expect, test } from "bun:test";
+import type { AttachPreviewResponse } from "@autumn/shared";
+import { TestFeature } from "@tests/setup/v2Features.js";
+import { hoursToFinalizeInvoice } from "@tests/utils/constants.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { advanceTestClock } from "@tests/utils/stripeUtils.js";
+import ctx from "@tests/utils/testInitUtils/createTestContext.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+import { addHours, addMonths } from "date-fns";
+import { createStripeCli } from "@/external/connect/createStripeCli.js";
+import { createPercentCoupon } from "../utils/discounts/discountTestUtils.js";
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits discount 1: catalog fallback when no stored row exists")}`,
+	async () => {
+		const customerId = "imc-disc-fallback";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV2_2 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro, premium] }),
+			],
+			actions: [s.billing.attach({ productId: pro.id })],
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		expect(preview.line_items.length).toBeGreaterThan(0);
+		expect(preview.total).toBeDefined();
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThanOrEqual(-20);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits discount 2: discounted quantity decrease — refund based on stored discounted charge")}`,
+	async () => {
+		const customerId = "imc-disc-qty-dec";
+
+		const billingUnits = 100;
+		const pricePerPack = 10;
+
+		const prepaidMessages = items.prepaidMessages({
+			includedUsage: 0,
+			billingUnits,
+			price: pricePerPack,
+		});
+
+		const product = products.pro({
+			id: "prepaid-disc",
+			items: [prepaidMessages],
+		});
+
+		const initialQuantity = 500;
+		const decreasedQuantity = 200;
+
+		const { autumnV1, testClockId, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [product] }),
+			],
+			actions: [],
+		});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `prepaid-disc_${customerId}`,
+			options: [
+				{ feature_id: TestFeature.Messages, quantity: initialQuantity },
+			],
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = await autumnV1.subscriptions.previewUpdate({
+			customer_id: customerId,
+			product_id: `prepaid-disc_${customerId}`,
+			options: [
+				{
+					feature_id: TestFeature.Messages,
+					quantity: decreasedQuantity,
+				},
+			],
+		});
+
+		expect(preview.total).toBeLessThan(0);
+
+		const fullPriceRefundBound =
+			-((initialQuantity - decreasedQuantity) / billingUnits) * pricePerPack;
+		expect(preview.total).toBeGreaterThan(fullPriceRefundBound);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits discount 3: trial sibling with discount — credit reflects discounted charge")}`,
+	async () => {
+		const customerId = "imc-disc-trial-sib";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premiumTrial = products.premiumWithTrial({
+			id: "premium-trial",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+			trialDays: 14,
+			cardRequired: false,
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premiumTrial] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium-trial_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-20);
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `premium-trial_${customerId}`,
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 4000));
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits discount 4: discounted credit magnitude bounded by stored charge")}`,
+	async () => {
+		const customerId = "imc-disc-no-double";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-16.01);
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(result.invoice?.total).toBeCloseTo(preview.total, 0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/downgrades.test.ts

@@ -0,0 +1,171 @@
+/**
+ * Invoice-Matched Proration Credits — Downgrade Tests
+ *
+ * Verifies that scheduled downgrade previews source outgoing credits from
+ * stored invoice line items (actual charged amounts) rather than catalog prices.
+ *
+ * - With discount: outgoing credit reflects the discounted charge ($40, not $50)
+ * - Without discount: outgoing credit reflects the full catalog charge ($50)
+ */
+
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3 } from "@autumn/shared";
+import { expectCustomerInvoiceCorrect } from "@tests/integration/billing/utils/expectCustomerInvoiceCorrect";
+import { expectPreviewNextCycleCorrect } from "@tests/integration/billing/utils/expectPreviewNextCycleCorrect";
+import { items } from "@tests/utils/fixtures/items";
+import { products } from "@tests/utils/fixtures/products";
+import { advanceTestClock } from "@tests/utils/stripeUtils";
+import { advanceToNextInvoice } from "@tests/utils/testAttachUtils/testAttachUtils";
+import ctx from "@tests/utils/testInitUtils/createTestContext";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario";
+import chalk from "chalk";
+import { createStripeCli } from "@/external/connect/createStripeCli";
+import { createPercentCoupon } from "../utils/discounts/discountTestUtils";
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 1: Scheduled downgrade with discount — outgoing credit reflects discounted price
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits downgrade 1: scheduled downgrade with discount — next_cycle outgoing credit reflects discounted price")}`,
+	async () => {
+		const customerId = "imc-down-disc";
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ paymentMethod: "success" }),
+					s.products({ list: [premium, pro] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({
+			stripeCli,
+			percentOff: 20,
+		});
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: premium.id,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customerAfterAttach =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterAttach,
+			count: 1,
+			latestTotal: 40,
+		});
+
+		const renewedAt = await advanceToNextInvoice({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			currentEpochMs: advancedTo,
+		});
+
+		const customerAfterRenewal =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterRenewal,
+			count: 2,
+			latestTotal: 40,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewedAt),
+			numberOfDays: 5,
+		});
+
+		const preview = await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `pro_${customerId}`,
+		});
+
+		expect(preview.total).toBe(0);
+
+		const nextCycle = expectPreviewNextCycleCorrect({
+			preview,
+			expectDefined: true,
+		})!;
+
+		expect(nextCycle.total).toBeLessThan(50);
+		expect(nextCycle.total).toBeGreaterThan(0);
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 2: Scheduled downgrade without discount — outgoing credit reflects full price
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits downgrade 2: scheduled downgrade without discount — next_cycle outgoing credit reflects full price")}`,
+	async () => {
+		const customerId = "imc-down-full";
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, autumnV2_2 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [premium, pro] }),
+			],
+			actions: [
+				s.billing.attach({ productId: premium.id }),
+				s.advanceToNextInvoice(),
+				s.advanceTestClock({ days: 5 }),
+			],
+		});
+
+		const customerAfterRenewal =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterRenewal,
+			count: 2,
+			latestTotal: 50,
+		});
+
+		const preview = await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `pro_${customerId}`,
+		});
+
+		expect(preview.total).toBe(0);
+
+		const nextCycle = expectPreviewNextCycleCorrect({
+			preview,
+			expectDefined: true,
+		})!;
+
+		expect(nextCycle.total).toBeLessThan(50);
+		expect(nextCycle.total).toBeGreaterThan(0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/edge-cases.test.ts

@@ -0,0 +1,281 @@
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3 } from "@autumn/shared";
+import { expectCustomerFeatureCorrect } from "@tests/integration/billing/utils/expectCustomerFeatureCorrect.js";
+import { expectCustomerInvoiceCorrect } from "@tests/integration/billing/utils/expectCustomerInvoiceCorrect.js";
+import {
+	expectCustomerProducts,
+	expectProductActive,
+} from "@tests/integration/billing/utils/expectCustomerProductCorrect.js";
+import { TestFeature } from "@tests/setup/v2Features.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 1: Catalog fallback when no stored row exists
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched edge 1: catalog fallback when no stored row exists")}`,
+	async () => {
+		const customerId = "inv-match-edge-fallback";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [pro, premium] }),
+			],
+			actions: [s.billing.attach({ productId: pro.id })],
+		});
+
+		const upgradeResult = await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: premium.id,
+		});
+
+		expect(upgradeResult).toBeDefined();
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+
+		await expectCustomerProducts({
+			customer,
+			active: [premium.id],
+			notPresent: [pro.id],
+		});
+
+		expectCustomerFeatureCorrect({
+			customer,
+			featureId: TestFeature.Messages,
+			includedUsage: 1000,
+			balance: 1000,
+			usage: 0,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer,
+			count: 2,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 2: Multi-attach with outgoing credit
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched edge 2: multi-attach with outgoing credit from stored charge")}`,
+	async () => {
+		const customerId = "inv-match-edge-multi";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const addon = products.recurringAddOn({
+			id: "addon",
+			items: [items.monthlyWords({ includedUsage: 200 })],
+		});
+
+		const { autumnV1, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success", testClock: true }),
+				s.products({ list: [pro, premium, addon] }),
+			],
+			actions: [
+				s.billing.attach({ productId: pro.id }),
+				s.advanceTestClock({ months: 1 }),
+				s.advanceTestClock({ days: 15 }),
+			],
+		});
+
+		const customerBefore =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		const invoiceCountBefore = customerBefore.invoices?.length ?? 0;
+
+		const preview = await autumnV1.billing.previewMultiAttach({
+			customer_id: customerId,
+			plans: [{ plan_id: premium.id }, { plan_id: addon.id }],
+		});
+
+		expect(preview.total).toBeDefined();
+		expect(preview.outgoing.length).toBeGreaterThanOrEqual(1);
+
+		const outgoingPro = preview.outgoing.find((c: { plan_id: string }) => c.plan_id === pro.id);
+		expect(outgoingPro).toBeDefined();
+
+		await autumnV1.billing.multiAttach({
+			customer_id: customerId,
+			plans: [{ plan_id: premium.id }, { plan_id: addon.id }],
+		});
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+
+		await expectCustomerProducts({
+			customer,
+			active: [premium.id, addon.id],
+			notPresent: [pro.id],
+		});
+
+		expectCustomerFeatureCorrect({
+			customer,
+			featureId: TestFeature.Messages,
+			includedUsage: 1000,
+		});
+
+		expectCustomerFeatureCorrect({
+			customer,
+			featureId: TestFeature.Words,
+			includedUsage: 200,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer,
+			count: invoiceCountBefore + 1,
+		});
+
+		const latestInvoice = customer.invoices?.[0];
+		expect(latestInvoice).toBeDefined();
+		expect(latestInvoice!.total).toBeDefined();
+
+		expect(latestInvoice!.total).toBeLessThan(70);
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 3: No-op re-attach — filterUnchangedPrices cancels
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched edge 3: no-op re-attach — filterUnchangedPrices cancels")}`,
+	async () => {
+		const customerId = "inv-match-edge-noop";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success", testClock: true }),
+				s.products({ list: [pro] }),
+			],
+			actions: [
+				s.billing.attach({ productId: pro.id }),
+				s.advanceTestClock({ months: 1 }),
+			],
+		});
+
+		await expectProductActive({
+			customer: await autumnV1.customers.get<ApiCustomerV3>(customerId),
+			productId: pro.id,
+		});
+
+		let threw = false;
+		try {
+			await autumnV1.billing.previewAttach({
+				customer_id: customerId,
+				product_id: pro.id,
+			});
+		} catch (err: any) {
+			threw = true;
+			expect(err.code).toBe("plan_already_attached");
+		}
+		expect(threw).toBe(true);
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 4: Non-USD currency rounding (EUR)
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched edge 4: non-USD currency — EUR upgrade rounding")}`,
+	async () => {
+		const customerId = "inv-match-edge-eur";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success", testClock: true }),
+				s.products({ list: [pro, premium] }),
+			],
+			actions: [
+				s.billing.attach({ productId: pro.id }),
+				s.advanceTestClock({ months: 1 }),
+				s.advanceTestClock({ days: 15 }),
+			],
+		});
+
+		const customerBefore =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		const invoiceCountBefore = customerBefore.invoices?.length ?? 0;
+
+		const preview = await autumnV1.billing.previewAttach({
+			customer_id: customerId,
+			product_id: premium.id,
+		});
+
+		expect(preview.total).toBeDefined();
+		expect(preview.total).toBeGreaterThan(0);
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: premium.id,
+		});
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+
+		await expectCustomerProducts({
+			customer,
+			active: [premium.id],
+			notPresent: [pro.id],
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer,
+			count: invoiceCountBefore + 1,
+		});
+
+		const latestInvoice = customer.invoices?.[0];
+		expect(latestInvoice).toBeDefined();
+		expect(latestInvoice!.total).toBeCloseTo(preview.total, 0);
+
+		const diff = Math.abs(latestInvoice!.total - preview.total);
+		expect(diff).toBeLessThanOrEqual(0.01);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/entities.test.ts

@@ -0,0 +1,203 @@
+import { expect, test } from "bun:test";
+import type { AttachPreviewResponse } from "@autumn/shared";
+import { TestFeature } from "@tests/setup/v2Features.js";
+import { hoursToFinalizeInvoice } from "@tests/utils/constants.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { advanceTestClock } from "@tests/utils/stripeUtils.js";
+import ctx from "@tests/utils/testInitUtils/createTestContext.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+import { addHours, addMonths } from "date-fns";
+import { createStripeCli } from "@/external/connect/createStripeCli.js";
+import { createPercentCoupon } from "../utils/discounts/discountTestUtils.js";
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits entities 1: single entity upgrade — credit from stored charge")}`,
+	async () => {
+		const customerId = "imc-ent-single-upg";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, entities, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+					s.entities({ count: 1, featureId: TestFeature.Users }),
+				],
+				actions: [
+					s.billing.attach({ productId: pro.id, entityIndex: 0 }),
+				],
+			});
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+			entity_id: entities[0].id,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-20);
+
+		expect(preview.total).toBeDefined();
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits entities 2: entity with discount — credit reflects discounted amount")}`,
+	async () => {
+		const customerId = "imc-ent-disc-upg";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, entities, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+					s.entities({ count: 1, featureId: TestFeature.Users }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			entity_id: entities[0].id,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+			entity_id: entities[0].id,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-16.01);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits entities 3: entity add mid-cycle — no credit for new entity")}`,
+	async () => {
+		const customerId = "imc-ent-add-midcycle";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, entities, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro] }),
+					s.entities({ count: 2, featureId: TestFeature.Users }),
+				],
+				actions: [
+					s.billing.attach({ productId: pro.id, entityIndex: 0 }),
+				],
+			});
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const result = await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			entity_id: entities[1].id,
+		});
+
+		const creditLines = (result.invoice?.line_items ?? []).filter(
+			(li: { total: number }) => li.total < 0,
+		);
+		expect(creditLines.length).toBe(0);
+
+		expect(result.invoice?.total).toBeGreaterThanOrEqual(0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/multi-attach.test.ts

@@ -0,0 +1,157 @@
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3 } from "@autumn/shared";
+import {
+	expectCustomerProducts,
+	expectProductActive,
+} from "@tests/integration/billing/utils/expectCustomerProductCorrect.js";
+import { hoursToFinalizeInvoice } from "@tests/utils/constants.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { advanceTestClock } from "@tests/utils/stripeUtils.js";
+import ctx from "@tests/utils/testInitUtils/createTestContext.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+import { addHours, addMonths } from "date-fns";
+import { createStripeCli } from "@/external/connect/createStripeCli.js";
+import { createPercentCoupon } from "../utils/discounts/discountTestUtils.js";
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits multi-attach 1: discounted outgoing — credit reflects stored charge")}`,
+	async () => {
+		const customerId = "imc-multi-disc-out";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const addon = products.recurringAddOn({
+			id: "addon",
+			items: [items.monthlyWords({ includedUsage: 200 })],
+		});
+
+		const { autumnV1, testClockId, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro, premium, addon] }),
+			],
+			actions: [],
+		});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = await autumnV1.billing.previewMultiAttach({
+			customer_id: customerId,
+			plans: [{ plan_id: `premium_${customerId}` }, { plan_id: `addon_${customerId}` }],
+		});
+
+		expect(preview.total).toBeDefined();
+		expect(preview.outgoing.length).toBeGreaterThanOrEqual(1);
+
+		const outgoingPro = preview.outgoing.find(
+			(c: { plan_id: string }) => c.plan_id === `pro_${customerId}`,
+		);
+		expect(outgoingPro).toBeDefined();
+
+		const catalogTotal = 50 + 20;
+		expect(preview.total).toBeLessThan(catalogTotal);
+
+		await autumnV1.billing.multiAttach({
+			customer_id: customerId,
+			plans: [{ plan_id: `premium_${customerId}` }, { plan_id: `addon_${customerId}` }],
+		});
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+
+		await expectCustomerProducts({
+			customer,
+			active: [`premium_${customerId}`, `addon_${customerId}`],
+			notPresent: [`pro_${customerId}`],
+		});
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits multi-attach 2: add-only — no credit lines")}`,
+	async () => {
+		const customerId = "imc-multi-add-only";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const addon = products.recurringAddOn({
+			id: "addon",
+			items: [items.monthlyWords({ includedUsage: 200 })],
+		});
+
+		const { autumnV1 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro, addon] }),
+			],
+			actions: [s.billing.attach({ productId: pro.id })],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `addon_${customerId}`,
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+
+		await expectProductActive({
+			customer,
+			productId: `pro_${customerId}`,
+		});
+
+		await expectProductActive({
+			customer,
+			productId: `addon_${customerId}`,
+		});
+
+		const latestInvoice = customer.invoices?.[0];
+		expect(latestInvoice).toBeDefined();
+		expect(latestInvoice!.total).toBeGreaterThanOrEqual(0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/quantity.test.ts

@@ -0,0 +1,85 @@
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3 } from "@autumn/shared";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { advanceTestClock } from "@tests/utils/stripeUtils.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched qty 1: prepaid quantity decrease — credit from stored charge")}`,
+	async () => {
+		const customerId = "inv-match-qty-decrease";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, testClockId, ctx } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro] }),
+			],
+			actions: [s.billing.attach({ productId: "pro" })],
+		});
+
+		let advancedTo = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId as string,
+			numberOfMonths: 1,
+			waitForSeconds: 30,
+		});
+		advancedTo = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId as string,
+			startingFrom: new Date(advancedTo),
+			numberOfDays: 15,
+			waitForSeconds: 20,
+		});
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		expect(customer.products.length).toBeGreaterThan(0);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched qty 2: prepaid quantity decrease then increase — netting")}`,
+	async () => {
+		const customerId = "inv-match-qty-netting";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const { autumnV1, testClockId, ctx } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro] }),
+			],
+			actions: [s.billing.attach({ productId: "pro" })],
+		});
+
+		let advancedTo = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId as string,
+			numberOfMonths: 1,
+			waitForSeconds: 30,
+		});
+		advancedTo = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId as string,
+			startingFrom: new Date(advancedTo),
+			numberOfDays: 15,
+			waitForSeconds: 20,
+		});
+
+		const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		expect(customer.products.length).toBeGreaterThan(0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/trials.test.ts

@@ -0,0 +1,252 @@
+/**
+ * Invoice-Matched Proration Credits — Trial Tests
+ *
+ * Verifies correct credit behavior when trials interact with the
+ * invoice-matched credit system:
+ *
+ * - Upgrade during trial: no credit (no stored charge for a $0 trial)
+ * - Paid product switched to trial sibling: paid product credited from stored charge
+ * - End trial: no refund-direction line items emitted
+ */
+
+import { expect, test } from "bun:test";
+import type { ApiCustomerV3 } from "@autumn/shared";
+import { expectCustomerInvoiceCorrect } from "@tests/integration/billing/utils/expectCustomerInvoiceCorrect";
+import {
+	expectCustomerProducts,
+	expectProductActive,
+} from "@tests/integration/billing/utils/expectCustomerProductCorrect";
+import {
+	expectProductNotTrialing,
+	expectProductTrialing,
+} from "@tests/integration/billing/utils/expectCustomerProductTrialing";
+import { expectPreviewNextCycleCorrect } from "@tests/integration/billing/utils/expectPreviewNextCycleCorrect";
+import { items } from "@tests/utils/fixtures/items";
+import { products } from "@tests/utils/fixtures/products";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario";
+import chalk from "chalk";
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 1: Upgrade during trial — no credit (trial product has no stored charge)
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits trial 1: upgrade during trial — no credit for outgoing trial product")}`,
+	async () => {
+		const customerId = "imc-trial-upgrade";
+
+		const proTrial = products.proWithTrial({
+			id: "pro-trial",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+			trialDays: 14,
+			cardRequired: false,
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [proTrial, premium] }),
+			],
+			actions: [s.billing.attach({ productId: proTrial.id })],
+		});
+
+		const customerTrialing =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerProducts({
+			customer: customerTrialing,
+			active: [proTrial.id],
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerTrialing,
+			count: 1,
+			latestTotal: 0,
+		});
+
+		const preview = await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(preview.total).toBe(50);
+
+		const creditLines = preview.line_items.filter((li: { total: number }) => li.total < 0);
+		expect(creditLines.length).toBe(0);
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: premium.id,
+		});
+
+		const customerAfterUpgrade =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerProducts({
+			customer: customerAfterUpgrade,
+			active: [premium.id],
+			notPresent: [proTrial.id],
+		});
+
+		await expectProductNotTrialing({
+			customer: customerAfterUpgrade,
+			productId: premium.id,
+			nowMs: advancedTo,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterUpgrade,
+			count: 2,
+			latestTotal: 50,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 2: Paid product switched to trial sibling — sibling credited from stored charge
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits trial 2: paid product switched to trial — credit from stored charge")}`,
+	async () => {
+		const customerId = "imc-trial-sibling";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premiumTrial = products.premiumWithTrial({
+			id: "premium-trial",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+			trialDays: 14,
+			cardRequired: true,
+		});
+
+		const { autumnV1, autumnV2_2, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [pro, premiumTrial] }),
+			],
+			actions: [s.billing.attach({ productId: pro.id })],
+		});
+
+		const customerAfterAttach =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductActive({
+			customer: customerAfterAttach,
+			productId: pro.id,
+		});
+		await expectCustomerInvoiceCorrect({
+			customer: customerAfterAttach,
+			count: 1,
+			latestTotal: 20,
+		});
+
+		const preview = await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium-trial_${customerId}`,
+		});
+
+		expect(preview.total).toBe(-20);
+
+		const creditLines = preview.line_items.filter((li: { total: number }) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum: number, li: { total: number }) => sum + li.total, 0);
+		expect(creditTotal).toBe(-20);
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: premiumTrial.id,
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 4000));
+
+		const customerAfterSwitch =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectCustomerProducts({
+			customer: customerAfterSwitch,
+			active: [premiumTrial.id],
+			notPresent: [pro.id],
+		});
+
+		await expectProductTrialing({
+			customer: customerAfterSwitch,
+			productId: premiumTrial.id,
+			trialEndsAt: advancedTo + 14 * 24 * 60 * 60 * 1000,
+		});
+	},
+	300_000,
+);
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// TEST 3: End trial — no refund lines emitted
+// ═══════════════════════════════════════════════════════════════════════════════
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits trial 3: end trial — no refund-direction line items")}`,
+	async () => {
+		const customerId = "imc-trial-end";
+
+		const proTrial = products.proWithTrial({
+			id: "pro-trial",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+			trialDays: 7,
+			cardRequired: true,
+		});
+
+		const { autumnV1, autumnV2_2, advancedTo } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ paymentMethod: "success" }),
+				s.products({ list: [proTrial] }),
+			],
+			actions: [s.billing.attach({ productId: proTrial.id })],
+		});
+
+		const customerTrialing =
+			await autumnV1.customers.get<ApiCustomerV3>(customerId);
+		await expectProductTrialing({
+			customer: customerTrialing,
+			productId: proTrial.id,
+			trialEndsAt: advancedTo + 7 * 24 * 60 * 60 * 1000,
+		});
+
+		await expectCustomerInvoiceCorrect({
+			customer: customerTrialing,
+			count: 1,
+			latestTotal: 0,
+		});
+
+		const previewBeforeTrialEnd = await autumnV2_2.subscriptions.previewUpdate({
+			customer_id: customerId,
+			product_id: proTrial.id,
+			recalculate_balances: { enabled: true },
+		});
+
+		const refundLines = previewBeforeTrialEnd.line_items.filter(
+			(li: { total: number }) => li.total < 0,
+		);
+		expect(refundLines.length).toBe(0);
+
+		const nextCyclePreview = expectPreviewNextCycleCorrect({
+			preview: previewBeforeTrialEnd,
+			expectDefined: true,
+		})!;
+
+		const nextCycleRefundLines = nextCyclePreview.line_items.filter(
+			(li) => li.total < 0,
+		);
+		expect(nextCycleRefundLines.length).toBe(0);
+
+		expect(nextCyclePreview.total).toBeGreaterThanOrEqual(0);
+	},
+	300_000,
+);

server/tests/integration/billing/invoice-matched-credits/upgrades.test.ts

@@ -0,0 +1,355 @@
+import { expect, test } from "bun:test";
+import type { AttachPreviewResponse } from "@autumn/shared";
+import { hoursToFinalizeInvoice } from "@tests/utils/constants.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import { advanceTestClock } from "@tests/utils/stripeUtils.js";
+import ctx from "@tests/utils/testInitUtils/createTestContext.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+import { addHours, addMonths } from "date-fns";
+import { createStripeCli } from "@/external/connect/createStripeCli.js";
+import {
+	createAmountCoupon,
+	createPercentCoupon,
+} from "../utils/discounts/discountTestUtils.js";
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits upgrade 1: percent-off forever discount — credit reflects discounted price")}`,
+	async () => {
+		const customerId = "inv-cred-upg-pct";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeCloseTo(-8, 0);
+
+		for (const creditLine of creditLines) {
+			const discounts = creditLine.discounts ?? [];
+			expect(discounts.length).toBe(0);
+		}
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(result.invoice?.total).toBeCloseTo(preview.total, 0);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits upgrade 2: no discount — credit reflects full price")}`,
+	async () => {
+		const customerId = "inv-cred-upg-full";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV2_2 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro, premium] }),
+			],
+			actions: [
+				s.billing.attach({ productId: pro.id }),
+				s.advanceTestClock({ toNextInvoice: true }),
+				s.advanceTestClock({ days: 15 }),
+			],
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-20);
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(result.invoice?.total).toBeCloseTo(preview.total, 0);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits upgrade 3: amount-off coupon — credit reflects discounted price")}`,
+	async () => {
+		const customerId = "inv-cred-upg-amt";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createAmountCoupon({
+			stripeCli,
+			amountOffCents: 500,
+		});
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const renewalTime = await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			startingFrom: new Date(renewalTime),
+			numberOfDays: 15,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-15);
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(result.invoice?.total).toBeCloseTo(preview.total, 0);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits upgrade 4: at cycle start — full credit equals full charged amount")}`,
+	async () => {
+		const customerId = "inv-cred-upg-start";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const { autumnV1, autumnV2_2, testClockId, advancedTo } =
+			await initScenario({
+				customerId,
+				setup: [
+					s.customer({ testClock: true, paymentMethod: "success" }),
+					s.products({ list: [pro, premium] }),
+				],
+				actions: [],
+			});
+
+		const stripeCli = createStripeCli({ org: ctx.org, env: ctx.env });
+		const coupon = await createPercentCoupon({ stripeCli, percentOff: 20 });
+
+		await autumnV1.billing.attach({
+			customer_id: customerId,
+			product_id: `pro_${customerId}`,
+			discounts: [{ reward_id: coupon.id }],
+		});
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		await advanceTestClock({
+			stripeCli: ctx.stripeCli,
+			testClockId: testClockId!,
+			advanceTo: addHours(
+				addMonths(new Date(advancedTo), 1),
+				hoursToFinalizeInvoice,
+			).getTime(),
+			waitForSeconds: 30,
+		});
+
+		const preview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = preview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const creditTotal = creditLines.reduce((sum, li) => sum + li.total, 0);
+		expect(creditTotal).toBeLessThan(0);
+		expect(creditTotal).toBeGreaterThan(-20.01);
+
+		const result = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(Math.abs((result.invoice?.total ?? 0) - preview.total)).toBeLessThan(
+			2,
+		);
+	},
+	300_000,
+);
+
+test.concurrent(
+	`${chalk.yellowBright("invoice-matched-credits upgrade 5: upgrade twice in one period — second upgrade nets prior refund")}`,
+	async () => {
+		const customerId = "inv-cred-upg-twice";
+
+		const pro = products.pro({
+			id: "pro",
+			items: [items.monthlyMessages({ includedUsage: 500 })],
+		});
+
+		const premium = products.premium({
+			id: "premium",
+			items: [items.monthlyMessages({ includedUsage: 1000 })],
+		});
+
+		const growth = products.growth({
+			id: "growth",
+			items: [items.monthlyMessages({ includedUsage: 2000 })],
+		});
+
+		const { autumnV2_2 } = await initScenario({
+			customerId,
+			setup: [
+				s.customer({ testClock: true, paymentMethod: "success" }),
+				s.products({ list: [pro, premium, growth] }),
+			],
+			actions: [
+				s.billing.attach({ productId: pro.id }),
+				s.advanceTestClock({ toNextInvoice: true }),
+				s.advanceTestClock({ days: 10 }),
+			],
+		});
+
+		const firstUpgradeResult = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `premium_${customerId}`,
+		});
+
+		expect(firstUpgradeResult.invoice).toBeDefined();
+
+		await new Promise((resolve) => setTimeout(resolve, 5000));
+
+		const secondPreview = (await autumnV2_2.billing.previewAttach({
+			customer_id: customerId,
+			plan_id: `growth_${customerId}`,
+		})) as AttachPreviewResponse;
+
+		const creditLines = secondPreview.line_items.filter((li) => li.total < 0);
+		expect(creditLines.length).toBeGreaterThan(0);
+
+		const positiveLines = secondPreview.line_items.filter((li) => li.total > 0);
+		expect(positiveLines.length).toBeGreaterThan(0);
+
+		const secondResult = await autumnV2_2.billing.attach({
+			customer_id: customerId,
+			plan_id: `growth_${customerId}`,
+		});
+
+		expect(secondResult.invoice?.total).toBeCloseTo(secondPreview.total, 0);
+	},
+	300_000,
+);

server/tests/unit/billing/invoice-matched-credits/invoice-credit-matcher.spec.ts

@@ -0,0 +1,201 @@
+import { describe, expect, test } from "bun:test";
+import type { DbInvoiceLineItem } from "@autumn/shared";
+import chalk from "chalk";
+import {
+	computeAlreadyRefundedForCharge,
+	computeProratedCredit,
+	splitMultiEntityAmount,
+} from "@/internal/billing/v2/utils/lineItems/storedLineItemUtils";
+
+const PERIOD_START = 1_700_000_000_000;
+const PERIOD_END = PERIOD_START + 30 * 24 * 60 * 60 * 1000;
+const MID_CYCLE = PERIOD_START + 15 * 24 * 60 * 60 * 1000;
+
+const makeChargeRow = (
+	overrides: Partial<DbInvoiceLineItem> = {},
+): DbInvoiceLineItem =>
+	({
+		id: "li_charge_1",
+		amount: 20,
+		amount_after_discounts: 20,
+		effective_period_start: PERIOD_START,
+		effective_period_end: PERIOD_END,
+		customer_product_ids: ["cp_1"],
+		price_id: "price_pro",
+		stripe_price_id: "stripe_price_pro",
+		direction: "charge",
+		discounts: [],
+		...overrides,
+	}) as DbInvoiceLineItem;
+
+const makeRefundRow = (
+	overrides: Partial<DbInvoiceLineItem> = {},
+): DbInvoiceLineItem =>
+	({
+		id: "li_refund_1",
+		amount: -10,
+		amount_after_discounts: -10,
+		effective_period_start: PERIOD_START,
+		effective_period_end: PERIOD_END,
+		customer_product_ids: ["cp_1"],
+		price_id: "price_pro",
+		stripe_price_id: "stripe_price_pro",
+		direction: "refund",
+		discounts: [],
+		...overrides,
+	}) as DbInvoiceLineItem;
+
+describe(chalk.yellowBright("computeProratedCredit"), () => {
+	test("prorates a full charge at mid-cycle to ~half negative", () => {
+		const result = computeProratedCredit({
+			chargeRow: makeChargeRow(),
+			now: MID_CYCLE,
+			alreadyRefunded: 0,
+		});
+
+		expect(result).toBeLessThan(0);
+		expect(result).toBeCloseTo(-10, 0);
+	});
+
+	test("returns 0 when period has ended", () => {
+		const result = computeProratedCredit({
+			chargeRow: makeChargeRow(),
+			now: PERIOD_END + 1000,
+			alreadyRefunded: 0,
+		});
+
+		expect(result).toBe(0);
+	});
+
+	test("returns 0 when period is null", () => {
+		const result = computeProratedCredit({
+			chargeRow: makeChargeRow({ effective_period_start: null }),
+			now: MID_CYCLE,
+			alreadyRefunded: 0,
+		});
+
+		expect(result).toBe(0);
+	});
+
+	test("subtracts already-refunded before prorating", () => {
+		const fullCredit = computeProratedCredit({
+			chargeRow: makeChargeRow({ amount_after_discounts: 20 }),
+			now: MID_CYCLE,
+			alreadyRefunded: 0,
+		});
+
+		const partialCredit = computeProratedCredit({
+			chargeRow: makeChargeRow({ amount_after_discounts: 20 }),
+			now: MID_CYCLE,
+			alreadyRefunded: 10,
+		});
+
+		expect(Math.abs(partialCredit)).toBeLessThan(Math.abs(fullCredit));
+	});
+
+	test("returns 0 when fully refunded", () => {
+		const result = computeProratedCredit({
+			chargeRow: makeChargeRow({ amount_after_discounts: 20 }),
+			now: MID_CYCLE,
+			alreadyRefunded: 20,
+		});
+
+		expect(result).toBe(0);
+	});
+
+	test("uses amount_after_discounts (discounted charge gives smaller credit)", () => {
+		const fullPriceCredit = computeProratedCredit({
+			chargeRow: makeChargeRow({ amount_after_discounts: 20 }),
+			now: MID_CYCLE,
+			alreadyRefunded: 0,
+		});
+
+		const discountedCredit = computeProratedCredit({
+			chargeRow: makeChargeRow({ amount_after_discounts: 16 }),
+			now: MID_CYCLE,
+			alreadyRefunded: 0,
+		});
+
+		expect(Math.abs(discountedCredit)).toBeLessThan(Math.abs(fullPriceCredit));
+	});
+});
+
+describe(chalk.yellowBright("computeAlreadyRefundedForCharge"), () => {
+	test("sums matching refund rows by price and period", () => {
+		const result = computeAlreadyRefundedForCharge({
+			chargeRow: makeChargeRow(),
+			refundRows: [
+				makeRefundRow({ amount_after_discounts: -5 }),
+				makeRefundRow({ id: "li_refund_2", amount_after_discounts: -3 }),
+			],
+		});
+
+		expect(result).toBe(8);
+	});
+
+	test("excludes refunds with different price_id", () => {
+		const result = computeAlreadyRefundedForCharge({
+			chargeRow: makeChargeRow(),
+			refundRows: [
+				makeRefundRow({ price_id: "price_other", stripe_price_id: "other" }),
+			],
+		});
+
+		expect(result).toBe(0);
+	});
+
+	test("excludes refunds outside the charge period", () => {
+		const result = computeAlreadyRefundedForCharge({
+			chargeRow: makeChargeRow(),
+			refundRows: [
+				makeRefundRow({
+					effective_period_start: PERIOD_END + 1000,
+					effective_period_end: PERIOD_END + 30 * 24 * 60 * 60 * 1000,
+				}),
+			],
+		});
+
+		expect(result).toBe(0);
+	});
+
+	test("returns 0 with no refund rows", () => {
+		const result = computeAlreadyRefundedForCharge({
+			chargeRow: makeChargeRow(),
+			refundRows: [],
+		});
+
+		expect(result).toBe(0);
+	});
+});
+
+describe(chalk.yellowBright("splitMultiEntityAmount"), () => {
+	test("returns full amount for single cusProduct", () => {
+		const result = splitMultiEntityAmount(
+			makeChargeRow({ amount_after_discounts: 30 }),
+		);
+
+		expect(result).toBe(30);
+	});
+
+	test("splits evenly across multiple cusProduct ids", () => {
+		const result = splitMultiEntityAmount(
+			makeChargeRow({
+				amount_after_discounts: 30,
+				customer_product_ids: ["cp_1", "cp_2", "cp_3"],
+			}),
+		);
+
+		expect(result).toBe(10);
+	});
+
+	test("handles empty customer_product_ids", () => {
+		const result = splitMultiEntityAmount(
+			makeChargeRow({
+				amount_after_discounts: 30,
+				customer_product_ids: [],
+			}),
+		);
+
+		expect(result).toBe(30);
+	});
+});

shared/models/billingModels/context/billingContext.ts

@@ -10,6 +10,7 @@ import type {
 } from "@autumn/shared";
 import type { PaymentBehaviorIntent } from "@models/billingModels/context/paymentBehaviorIntent";
 import type { TransitionConfig } from "@models/billingModels/context/transitionConfig";
+import type { DbInvoiceLineItem } from "@models/cusModels/invoiceModels/invoiceLineItemTable";
 import type { EntInterval } from "@models/productModels/intervals/entitlementInterval";
 import type Stripe from "stripe";
 import { z } from "zod/v4";
@@ -112,6 +113,9 @@ export interface BillingContext {
 
 	anchorResetRefund?: AnchorResetRefund;
 
+	storedChargeLineItems?: DbInvoiceLineItem[];
+	storedRefundLineItems?: DbInvoiceLineItem[];
+
 	refundLastPayment?: "prorated" | "full";
 
 	paymentBehaviorIntent?: PaymentBehaviorIntent;

shared/utils/billingUtils/index.ts

@@ -7,6 +7,7 @@ export * from "./intervalUtils/intervalArithmetic";
 // Invoicing utils
 
 export * from "./invoicingUtils/backdateUtils/applyBackdatedLineItemAmount.js";
+export * from "./invoicingUtils/billingConstants.js";
 export * from "./invoicingUtils/filterUnchangedPricesFromLineItems.js";
 export * from "./invoicingUtils/lineItemBuilders/buildLineItem.js";
 export * from "./invoicingUtils/lineItemBuilders/fixedPriceToLineItem.js";

shared/utils/billingUtils/invoicingUtils/billingConstants.ts

@@ -0,0 +1 @@
+export const BILLING_AMOUNT_EPSILON = 0.01;

shared/utils/billingUtils/invoicingUtils/filterUnchangedPricesFromLineItems.ts

@@ -1,4 +1,5 @@
 import type { LineItem } from "@models/billingModels/lineItem/lineItem";
+import { BILLING_AMOUNT_EPSILON } from "./billingConstants";
 
 /**
  * Filters out line item pairs where a refund and charge item have the same price ID
@@ -32,10 +33,9 @@ export const filterUnchangedPricesFromLineItems = ({
 
 		if (matchingChargeIndex !== -1) {
 			const matchingChargeItem = chargeItems[matchingChargeIndex];
-			const total = refundItem.amount + matchingChargeItem.amount;
+			const netAmount = Math.abs(refundItem.amount + matchingChargeItem.amount);
 
-			if (total === 0) {
+			if (netAmount < BILLING_AMOUNT_EPSILON) {
-				// Amounts cancel out - mark charge item as matched (both will be removed)
 				matchedChargeIndices.add(matchingChargeIndex);
 				continue;
 			}