# Idempotency key

> Idempotency key — A unique value sent with a write request so a retried request is applied once — the API returns the original result instead of posting a second invoice, payment or journal.

Source: https://lopifi.com/glossary/idempotency-key
Part of: Lopifi — US GAAP books on autopilot, reviewed by a CPA (https://lopifi.com)

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**What is idempotency key?** In accounting, idempotency key means a unique value sent with a write request so a retried request is applied once — the API returns the original result instead of posting a second invoice, payment or journal.

## Words this system refuses for it

- transaction ID
- dedupe

- **Category:** Core ledger
- **Specified in:** [Lexicon](https://lopifi.com/md/docs/domain/11-lexicon)
- **Related:** invoice, journal, posting