> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.clearpay.co.uk/v-2/how-to-integrate/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.clearpay.co.uk/_mcp/server.

# How to Integrate

Our goal is to make upgrading to Express Checkout as simple as possible for existing Clearpay merchants. There are no new APIs. The only changes you need to make to your existing Clearpay  integration are:

1. Add Express Checkout button to the cart and/or product pages and configure JS with Clearpay  provided key
2. Update the `Create Checkout` and `Auth` (or `Capture Full Payment` if using the Immediate Payment Flow) API call payloads
3. Display the Clearpay Checkout Widget on a review page to enable dynamic updates to the order total after the Express Checkout flow (optional with Integrated Shipping)

![](file:docs/assets/images/924a0f1-AfterpayExpressHappyPath.png "AfterpayExpressHappyPath.png")

## Docs

- [Express Checkout Payload (Create Checkout)](https://developers.clearpay.co.uk/v-2/express-checkout-payload-create-checkout-2.md): 
- [Express Checkout Payload (Capture Full Payment)](https://developers.clearpay.co.uk/v-2/express-checkout-payload-capture-full-payment-2.md): 
- [Express Checkout Payload (Auth)](https://developers.clearpay.co.uk/v-2/express-checkout-payload-auth-2.md): 
- [Adding the Express Checkout Button](https://developers.clearpay.co.uk/v-2/adding-the-express-checkout-button-2.md): You must show a Clearpay checkout button on your cart and/or product pages to enable Express Checkout. When clicked, the Clearpay checkout button will start the checkout process in a popup flow (the redirect flow can optionally be used with Deferred Shipping).
- [Integrated Shipping](https://developers.clearpay.co.uk/v-2/integrated-shipping-2.md): 
- [Checkout Widget](https://developers.clearpay.co.uk/v-2/checkout-widget-2.md): 

## API Docs

- How to Integrate [Create Checkout [Express Checkout]](https://developers.clearpay.co.uk/v-2/how-to-integrate/create-checkout-express-checkout.md)
- How to Integrate [Capture Full Payment [Express Checkout]](https://developers.clearpay.co.uk/v-2/how-to-integrate/capture-full-payment-express-checkout-2.md)
- How to Integrate [Auth [Express Checkout]](https://developers.clearpay.co.uk/v-2/how-to-integrate/auth-express-checkout-2.md)

## OpenAPI Specification

The raw OpenAPI 3.1 specification for this API is available at:
- [OpenAPI JSON](https://developers.clearpay.co.uk/openapi.json)
- [OpenAPI YAML](https://developers.clearpay.co.uk/openapi.yaml)