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

# Set the webpage for payment links against a transaction

More easily work with multiple production environments that use separate domains by specifying a URL for an approved domain as the checkout payment link when creating a transaction.

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## What's new?

We made `transaction.checkout.url` a writeable field. You can pass a URL for an approved domain to this field when creating or updating a transaction to specify a URL to be used for the returned payment link for a transaction.

- **checkout** (object or null): Paddle Checkout details for this transaction.
  - **url** (string or null): Checkout URL to use for the payment link for this transaction. Pass the URL for an approved domain, or omit to use your default payment URL. Paddle returns a unique payment link composed of the URL passed or your default payment URL + `_?ptxn=` and the Paddle ID for this transaction.

## How it works

The `checkout.url` field against a transaction contains a link that Paddle generates that you can use to open a checkout for this transaction.

This link is composed of your default payment link + `_?ptxn=` and the Paddle ID for a transaction. Provided the default payment URL page [includes Paddle.js](https://developer.paddle.com/paddlejs/include-paddlejs.md), it automatically opens a checkout for the transaction passed in the URL.

Previously, `checkout.url` was a read-only field. This means that it was returned in responses from the API, but not valid if included in requests to the API.

With this update, you can pass a URL for an approved domain to `checkout.url` when creating or updating transactions. When included in requests, Paddle returns a `checkout.url` that's composed of the URL for the approved domain + `_?ptxn=` and the Paddle ID for a transaction.

If you don't include `checkout.url` in your request, Paddle returns a `checkout.url` composed using your default payment link as normal. When updating, you can pass `null` to `checkout.url` to set back to your default payment link.

{% callout type="info" %}
Only approved domains can be used for transaction payment links. View and request approval for domains in **Paddle > Checkout > Request domain approval**.

Domains on sandbox are automatically approved. If a domain in sandbox is pending, remove and re-add it.
{% /callout %}

## 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.

[Create](https://developer.paddle.com/api-reference/transactions/create-transaction.md) or [update a transaction](https://developer.paddle.com/api-reference/transactions/update-transaction.md) using the API to set `checkout.url` for a transaction.
## Summary of changes

| Name | Type | Change | Entity | Description |
| --- | --- | --- | --- | --- |
| `checkout.url` | Field | updated | Transaction | Writable on create and update; accepts a custom payment link domain. |