Add idempotency to your payments requests

Many Payments v3 API calls require idempotency.

The Payments API v3 supports API idempotency. This allows you to attempt to resend requests while only performing the requested action once, for as long as the key is valid.

For example, if there's a temporary connection issue, a request to create a payment could be safely retried several times without creating multiple payments.


Always use a different idempotency key for different requests

You must use different idempotency keys for different requests. Reusing the same idempotency key will cause any requests after the first to not be executed. If you try to reuse of an idempotency key with a different payload, while the key is still valid, you get an error response.

How to enable idempotency for requests

To use idempotency, where supported or required (for example, signed requests), add the Idempotency-Key header as shown in this example.

POST /v3/payments HTTP/1.1
Content-Type: application/json
Idempotency-Key: 3c9ae5ea-980f-4ebd-a027-04529942b95e
Tl-Signature: {Signature}
Authorization: Bearer {access_token}



We strongly advise that you use a UUID v4 for each idempotency key.
If you can't use a UUID and the endpoint doesn't require an authorisation token (such as the /v3/payments-provider-return endpoint), we recommend that you also include your client id in your idempotency key.

Scope and validity

Each idempotency key has a duration of 72 hours.

During the validity period, you can only send the same payload with the same idempotency key. If you do this, you receive an identical response.

If the payload is different, but the idempotency key is the same, you receive an error. The error type will usually be 422 or 409. See below for more information.

Error handling

These are some of the common errors associated with idempotency:

Error codeError typeDetailSolution
401UnauthenticatedInvalid request signature.Include the Idempotency-Key header in the JOSE headers of the signature when making requests to endpoints where idempotency is mandatory.
409Idempotency-Key Concurrency ConflictThe Idempotency-Key value is being used for a concurrent request.This error occurs because another request with the same idempotency key is in flight.

If you wait until the request is no longer in flight and make the same request with the same idempotency key, you receive an identical response.
422Idempotency-Key ReuseThe Idempotency-Key value has already been used for a different request.This should not happen if idempotent retries have been correctly implemented, so if this error is received it is advised not to attempt a retry.

In your idempotent retry implementation ensure that the request body is identical on retries.