> For the complete documentation index, see [llms.txt](https://startbutton.gitbook.io/startbutton-product-api/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://startbutton.gitbook.io/startbutton-product-api/getting-started/idempotency-and-rate-limits.md).

# Idempotency & Rate Limits

**Duplicate prevention:** Both collection and transfer requests use a `userTransactionReference` (reference) to prevent duplicate transactions. If you don't provide one, Startbutton generates a unique reference for you. If you provide one that's already been used, the request is rejected with a duplicate error. Your reference is returned in the webhook response as `userTransactionReference`.

**Rate limits:** All Startbutton API endpoints are limited to **1000 requests per minute**.