> For the complete documentation index, see [llms.txt](https://developer.paddle.com/llms.txt).

# Understand the impact of a subscription change when previewing

Check the update summary object returned when previewing an update to a subscription or billing for a one-time charge to get an overview of any prorated credits and charges created as a result of the change.

---

## What's new?

We added a new `update_summary` object to the response when working with the [preview an update to a subscription](https://developer.paddle.com/api-reference/subscriptions/preview-subscription.md) and [preview a one-time charge for a subscription](https://developer.paddle.com/api-reference/subscriptions/preview-subscription-charge.md) operations.

- **update_summary** (object): Impact of this subscription change. Includes whether the change results in a charge or credit, and totals for prorated amounts.
  - **credit** (object): Details of any credit adjustments created for this update. Paddle creates adjustments against existing transactions when prorating.
    - **amount** (string): Amount in the lowest denomination for the currency, e.g. 10 USD = 1000 (cents). Although represented as a string, this value must be a valid integer.
    - **currency_code** (string): Supported three-letter ISO 4217 currency code.
- **charge** (object): Details of the transaction to be created for this update. Paddle creates a transaction to bill for new charges.
  - **amount** (string): Amount in the lowest denomination for the currency, e.g. 10 USD = 1000 (cents). Although represented as a string, this value must be a valid integer.
  - **currency_code** (string): Supported three-letter ISO 4217 currency code.
- **result** (object): Details of the result of credits and charges. Where the total of any credit adjustments is greater than the total charge, the result is a prorated credit; otherwise, the result is a prorated charge.
  - **action** (string): Whether the subscription change results in a prorated credit or a charge.
  - **amount** (string): Amount representing the result of this update, either a charge or a credit.
  - **currency_code** (string): Three-letter ISO 4217 currency code for the transaction or adjustment.

## How it works

You can use the [preview an update to a subscription](https://developer.paddle.com/api-reference/subscriptions/preview-subscription.md) and [preview a one-time charge for a subscription](https://developer.paddle.com/api-reference/subscriptions/preview-subscription-charge.md) operations to preview a change to a subscription before making it.

The response includes `immediate_transaction`, `next_transaction`, and `recurring_transaction_details` objects, which let you preview any transactions created as a result of your change, as well as the impact on the regular amount that a customer is charged.

Previously, to determine whether a change resulted in a prorated charge or credit, you'd need to add up the totals of any `adjustments` and deduct from the total for the `immediate_transaction` or `next_transaction` total. If the result is negative, the change results in a prorated credit; if positive, a prorated charge.

The new `update_summary` object returns totals for prorated credits and charges, along with a `result` object that tells you whether the change results in a credit or charge overall. You don't need to do any of your own calculations.

## Next steps

This change is available in version `1` of the Paddle API.

It's a non-breaking change, meaning it doesn't impact existing integrations.

Use the [preview an update to a subscription](https://developer.paddle.com/api-reference/subscriptions/preview-subscription.md) and [preview a one-time charge for a subscription](https://developer.paddle.com/api-reference/subscriptions/preview-subscription-charge.md) operations to see the new `update_summary` object.
## Summary of changes

| Name | Type | Change | Entity | Description |
| --- | --- | --- | --- | --- |
| `update_summary` | Field | added | Subscription preview | Response object summarizing upcoming changes for preview operations. |