---
title: "Preview Update"
openapi: "openapi POST /v1/billing.preview_update"
---

import { DynamicParamField } from "/components/dynamic-param-field.jsx";
import { DynamicResponseField } from "/components/dynamic-response-field.jsx";
import { DynamicResponseExample } from "/components/dynamic-response-example.jsx";

### Body Parameters

<DynamicParamField body="customer_id" type="string" required>
  The ID of the customer to attach the plan to.
</DynamicParamField>

<DynamicParamField body="entity_id" type="string">
  The ID of the entity to attach the plan to.
</DynamicParamField>

<DynamicParamField body="plan_id" type="string" required>
  The ID of the plan.
</DynamicParamField>

<DynamicParamField body="feature_quantities" type="object[]">
  If this plan contains prepaid features, use this field to specify the quantity of each prepaid feature. This quantity includes the included amount and billing units defined when setting up the plan.
  <Expandable title="properties">
    <DynamicParamField body="feature_id" type="string" required>
      The ID of the feature to set quantity for.
    </DynamicParamField>

    <DynamicParamField body="quantity" type="number">
      The quantity of the feature.
    </DynamicParamField>

    <DynamicParamField body="adjustable" type="boolean">
      Whether the customer can adjust the quantity.
    </DynamicParamField>

  </Expandable>
</DynamicParamField>

<DynamicParamField body="version" type="number">
  The version of the plan to attach.
</DynamicParamField>

<DynamicParamField body="customize" type="object">
  Customize the plan to attach. Can override the price, items, free trial, or a combination.
  <Expandable title="properties">
    <DynamicParamField body="price" type="object | null">
      Base price configuration for a plan.
      <Expandable title="properties">
        <DynamicParamField body="amount" type="number" required>
          Base price amount for the plan.
        </DynamicParamField>

        <DynamicParamField body="interval" type="'one_off' | 'week' | 'month' | 'quarter' | 'semi_annual' | 'year'" required>
          Billing interval (e.g. 'month', 'year').
        </DynamicParamField>

        <DynamicParamField body="interval_count" type="number">
          Number of intervals per billing cycle. Defaults to 1.
        </DynamicParamField>

      </Expandable>
    </DynamicParamField>

    <DynamicParamField body="items" type="object[]">
      Override the items in the plan.
      <Expandable title="properties">
        <DynamicParamField body="feature_id" type="string" required>
          The ID of the feature to configure.
        </DynamicParamField>

        <DynamicParamField body="included" type="number">
          Number of free units included. Balance resets to this each interval for consumable features.
        </DynamicParamField>

        <DynamicParamField body="unlimited" type="boolean">
          If true, customer has unlimited access to this feature.
        </DynamicParamField>

        <DynamicParamField body="reset" type="object">
          Reset configuration for consumable features. Omit for non-consumable features like seats.
          <Expandable title="properties">
            <DynamicParamField body="interval" type="'one_off' | 'minute' | 'hour' | 'day' | 'week' | 'month' | 'quarter' | 'semi_annual' | 'year'" required>
              Interval at which balance resets (e.g. 'month', 'year'). For consumable features only.
            </DynamicParamField>

            <DynamicParamField body="interval_count" type="number">
              Number of intervals between resets. Defaults to 1.
            </DynamicParamField>

          </Expandable>
        </DynamicParamField>

        <DynamicParamField body="price" type="object">
          Pricing for usage beyond included units. Omit for free features.
          <Expandable title="properties">
            <DynamicParamField body="amount" type="number">
              Price per billing_units after included usage. Either 'amount' or 'tiers' is required.
            </DynamicParamField>

            <DynamicParamField body="tiers" type="object[]">
              Tiered pricing. Either 'amount' or 'tiers' is required.
              <Expandable title="properties">
                <DynamicParamField body="to" type="number" required />

                <DynamicParamField body="amount" type="number" required />

                <DynamicParamField body="flat_amount" type="number | null" />

              </Expandable>
            </DynamicParamField>

            <DynamicParamField body="tier_behavior" type="'graduated' | 'volume'" />

            <DynamicParamField body="interval" type="'one_off' | 'week' | 'month' | 'quarter' | 'semi_annual' | 'year'" required>
              Billing interval. For consumable features, should match reset.interval.
            </DynamicParamField>

            <DynamicParamField body="interval_count" type="number">
              Number of intervals per billing cycle. Defaults to 1.
            </DynamicParamField>

            <DynamicParamField body="billing_units" type="number">
              Units per price increment. Usage is rounded UP when billed (e.g. billing_units=100 means 101 rounds to 200).
            </DynamicParamField>

            <DynamicParamField body="billing_method" type="'prepaid' | 'usage_based'" required>
              'prepaid' for upfront payment (seats), 'usage_based' for pay-as-you-go.
            </DynamicParamField>

            <DynamicParamField body="max_purchase" type="number">
              Max units purchasable beyond included. E.g. included=100, max_purchase=300 allows 400 total.
            </DynamicParamField>

          </Expandable>
        </DynamicParamField>

        <DynamicParamField body="proration" type="object">
          Proration settings for prepaid features. Controls mid-cycle quantity change billing.
          <Expandable title="properties">
            <DynamicParamField body="on_increase" type="'bill_immediately' | 'prorate_immediately' | 'prorate_next_cycle' | 'bill_next_cycle'" required>
              Billing behavior when quantity increases mid-cycle.
            </DynamicParamField>

            <DynamicParamField body="on_decrease" type="'prorate' | 'prorate_immediately' | 'prorate_next_cycle' | 'none' | 'no_prorations'" required>
              Credit behavior when quantity decreases mid-cycle.
            </DynamicParamField>

          </Expandable>
        </DynamicParamField>

        <DynamicParamField body="rollover" type="object">
          Rollover config for unused units. If set, unused included units carry over.
          <Expandable title="properties">
            <DynamicParamField body="max" type="number">
              Max rollover units. Omit for unlimited rollover.
            </DynamicParamField>

            <DynamicParamField body="expiry_duration_type" type="'month' | 'forever'" required>
              When rolled over units expire.
            </DynamicParamField>

            <DynamicParamField body="expiry_duration_length" type="number">
              Number of periods before expiry.
            </DynamicParamField>

          </Expandable>
        </DynamicParamField>

      </Expandable>
    </DynamicParamField>

    <DynamicParamField body="free_trial" type="object | null">
      Free trial configuration for a plan.
      <Expandable title="properties">
        <DynamicParamField body="duration_length" type="number" required>
          Number of duration_type periods the trial lasts.
        </DynamicParamField>

        <DynamicParamField body="duration_type" type="'day' | 'month' | 'year'">
          Unit of time for the trial ('day', 'month', 'year').
        </DynamicParamField>

        <DynamicParamField body="card_required" type="boolean">
          If true, payment method required to start trial. Customer is charged after trial ends.
        </DynamicParamField>

      </Expandable>
    </DynamicParamField>

  </Expandable>
</DynamicParamField>

<DynamicParamField body="invoice_mode" type="object">
  Invoice mode creates a draft or open invoice and sends it to the customer, instead of charging their card immediately. This uses Stripe's send_invoice collection method.
  <Expandable title="properties">
    <DynamicParamField body="enabled" type="boolean" required>
      When true, creates an invoice and sends it to the customer instead of charging their card immediately. Uses Stripe's send_invoice collection method.
    </DynamicParamField>

    <DynamicParamField body="enable_plan_immediately" type="boolean">
      If true, enables the plan immediately even though the invoice is not paid yet.
    </DynamicParamField>

    <DynamicParamField body="finalize" type="boolean">
      If true, finalizes the invoice so it can be sent to the customer. If false, keeps it as a draft for manual review.
    </DynamicParamField>

  </Expandable>
</DynamicParamField>

<DynamicParamField body="proration_behavior" type="'prorate_immediately' | 'none'">
  How to handle proration when updating an existing subscription. 'prorate_immediately' charges/credits prorated amounts now, 'none' skips creating any charges.
</DynamicParamField>

<DynamicParamField body="cancel_action" type="'cancel_immediately' | 'cancel_end_of_cycle' | 'uncancel'">
  Action to perform for cancellation. 'cancel_immediately' cancels now with prorated refund, 'cancel_end_of_cycle' cancels at period end, 'uncancel' reverses a pending cancellation.
</DynamicParamField>


### Response

<DynamicResponseField name="customer_id" type="string">
  The ID of the customer.
</DynamicResponseField>

<DynamicResponseField name="line_items" type="object[]">
  List of line items for the current billing period.
  <Expandable title="properties">
    <DynamicResponseField name="title" type="string">
      The title of the line item.
    </DynamicResponseField>

    <DynamicResponseField name="description" type="string">
      A detailed description of the line item.
    </DynamicResponseField>

    <DynamicResponseField name="amount" type="number">
      The amount in cents for this line item.
    </DynamicResponseField>

    <DynamicResponseField name="discounts" type="object[]">
      List of discounts applied to this line item.
      <Expandable title="properties">
        <DynamicResponseField name="amountOff" type="number" />

        <DynamicResponseField name="percentOff" type="number" />

        <DynamicResponseField name="stripeCouponId" type="string" />

        <DynamicResponseField name="couponName" type="string" />

      </Expandable>
    </DynamicResponseField>

  </Expandable>
</DynamicResponseField>

<DynamicResponseField name="total" type="number">
  The total amount in cents for the current billing period.
</DynamicResponseField>

<DynamicResponseField name="currency" type="string">
  The three-letter ISO currency code (e.g., 'usd').
</DynamicResponseField>

<DynamicResponseField name="next_cycle" type="object">
  Preview of the next billing cycle, if applicable. This shows what the customer will be charged in subsequent cycles.
  <Expandable title="properties">
    <DynamicResponseField name="starts_at" type="number">
      Unix timestamp (milliseconds) when the next billing cycle starts.
    </DynamicResponseField>

    <DynamicResponseField name="total" type="number">
      The total amount in cents for the next cycle.
    </DynamicResponseField>

  </Expandable>
</DynamicResponseField>


<ResponseExample>
```json 200
{
  "customerId": "charles",
  "lineItems": [
    {
      "title": "Pro seed",
      "description": "Pro seed - Base Price (from 18 Feb 2026 to 18 Mar 2026)",
      "amount": 20,
      "discounts": []
    }
  ],
  "total": 20,
  "currency": "usd"
}
```
</ResponseExample>