Enable flexible behavior for subscriptions

Currently, credit proration amounts are calculated based on the value of the subscription item’s current price, tax, quantity, and the last discounts used.

You can configure billing_mode=flexible to enable a different proration logic that calculates credit prorations based on the original amount previously debited to a customer.

The current behavior could lead to unexpected prorations when a customer’s tax rates change, debit prorations are disabled, or complex amounts off coupons are used. The improved proration logic calculates credit prorations based only on the original amount previously debited to a customer. When a customer makes a change to their subscription that results in a credit, the proration is calculated using the amount they were previously billed, regardless of subsequent changes made to the subscription. Stripe recommends using billing_mode=flexible if the limitations of the public preview don’t apply to you.

Public preview limitations Public preview

During public preview, billing_mode=flexible isn’t compatible with all of Stripe Billing’s functionality.

When billing_mode=flexible is configured:

• Subscription Schedules are not supported.
• Usage-based billing is not supported.
• Automatic tax calculation is not supported.
• Trials are not supported.
• Quotes endpoints are not supported.
• You can’t reset the billing cycle anchor.
• You can’t create backdated subscriptions.
• You can’t pause payment collection on subscriptions.

If you use these features with billing_mode=flexible, they return a 400 error code.

Configure billing mode Public preview

You can configure billing_mode=flexible on specific subscriptions, and you can have multiple subscriptions with different billing_mode configurations. You can’t change the billing _mode after you set it (this ensures consistent logic and behavior throughout the lifecycle of each subscription).

When you configure billing_mode=flexible, it also updates subscription.trial_start to reflect the most recent trial start date.

Calculation logic with no prorations

In the following scenario, a 10 USD monthly subscription is upgraded to 20 USD with proration_behavior set to none for 10 days. There is no previous debit to base it on. Later, the subscription is downgraded to 10 USD a month with proration_behavior set to always_invoice.

To set up this scenario, first you create a subscription for 10 USD/month on 2025-04-01:

curl https://api.stripe.com/v1/subscriptions \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -d "items[0][price]"=price_10_monthly

The response includes the invoice that’s created for this subscription:

{
  id: "sub_123",
  latest_invoice: {
    id: "in_123",
    total: 10_00,
    currency: "usd"
    }
}

Then, on 2025-04-11, you upgrade the subscription to 20 USD/month without creating prorations:

curl https://api.stripe.com/v1/subscriptions/sub_123 \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -d "items[0][price]"=price_20_monthly \
  -d proration_behavior=none

You can see that the latest invoice is unchanged because proration_behavior is none:

{
  id: "sub_123",
  latest_invoice: {
    id: "in_123"
    }
}

Finally, on 2025-04-21, you downgrade the subscription to 10 USD/month and create prorations:

curl https://api.stripe.com/v1/subscriptions/sub_123 \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -d "items[0][price]"=price_10_monthly \
  -d proration_behavior=always_invoice

The default proration calculation logic creates a credit proration based on the current price, even though the customer never paid the 20 USD/month rate. The latest invoice credits a third of the month for 20 USD (-6.67 USD), even though the customer never paid for the price_20_monthly price. It also debits a third of the month for 10 USD (3.33 USD).

The calculation logic enabled with billing_mode=flexible creates a credit proration based on the last price billed for the subscription item. In this case, the latest invoice credits a third of a month for the 10 USD/month price billed on 2025-04-01 (3.33 USD) and debits a third of the month for the 10 USD price (3.33 USD). The credit and debit cancel out so the invoice total is 0 USD.

# Default behavior
# billing_mode = legacy_prorations
{
  id: "sub_123",
  latest_invoice: {
    id: "in_456",
    total: -3_34,
    currency: "usd"
    }
}

# New behavior
# billing_mode=flexible
{
  id: "sub_123",
  latest_invoice: {
    id: "in_456",
    total: 0,
    currency: "usd"
    }
}

Calculation logic for coupons applied to multiple subscription items

The amount_off coupon on the credit proration is weighted to prevent overbilling.

In the following scenario, a 5 USD coupon is unevenly allocated to a 25 USD monthly subscription for a 10 USD item and 20 USD item.

To set up this scenario, you create a subscription with multiple items and a coupon on 2025-02-01:

curl https://api.stripe.com/v1/subscriptions \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -d "items[0][price]"=price_20_monthly \
  -d "discounts[0][coupon]"=five_dollars_off

Which returns this response:

{
  id: "sub_123",
  latest_invoice: {
    id: "in_123",
    total: 25_00,
    currency: "usd",
    lines: {
      data: [
      {
        id: "ili_1",
        amount: 10_00,
        price: "price_10_monthly",
        discount_amounts: [{
          discount: "di_a",
          amount: 1_66 }] },
      {
        id: "ili_2",
        amount: 20_00,
        price: "price_20_monthly",
        discount_amounts: [{
          discount: "di_a",
          amount: 3_34
          }]
        },
    ] }
  }
}

To cancel the 10 USD/month subscription item using billing_mode=classic:

curl https://api.stripe.com/v1/subscription_items/si_10_monthly \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -d proration_behavior=create_prorations

To cancel the same item using billing_mode=flexible:

curl https://api.stripe.com/v1/subscription_items/si_10_monthly \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -d proration_behavior=create_prorations \
  -d billing_mode=flexible

The default behavior distributes a 5 USD coupon to each item (2.5 USD each), cancelling the cheaper item (5 USD) and resulting in a refund of 2.5 USD. The total has been calculated with the formula -0.5 x (10 USD price - 5 USD coupon) = -2.50 USD

The new behavior reflects the proportional discount applied to the canceled item, rather than potentially applying the full discount amount to the proration calculation. The total has been calculated using the formula -0.5 x (10 USD price - 1.66 USD discount amount) = -4.17 USD.

# Default behavior
# billing_mode = legacy_prorations
{
  "id": "sub_123",
  "latest_invoice": {
    "id": "in_456",
    "total": -250,
    "currency": "usd"
  }
}

# New behavior
# billing_mode = flexible
{
  "id": "sub_123",
  "latest_invoice": {
    "id": "in_789",
    "total": -417,
    "currency": "usd"
  }
}