Idempotency

When to use it

Two create endpoints support an idempotency key today:

• POST /api/v1/invoices
• POST /api/v1/payments-received

Use it whenever a create request might be retried after a timeout or dropped connection.

How it works

Send a unique value per create attempt:

Idempotency-Key: a1b2c3d4-...

A retry with the same key and the same body returns the original result instead of creating a duplicate. Reusing the same key with a different body returns 409 conflict.