Invoice API

Overview

An invoice API lets software create, retrieve, update, or track payment requests that specify an amount, currency, payer context, and lifecycle. An invoice API turns a commercial obligation into a machine-managed payment request. The invoice lifecycle may include created, pending, partially paid, paid, expired, canceled, refunded, or failed states. These states must not be inferred solely from a browser redirect. Observability for Invoice API should record operation, version, principal, request ID, latency, retry count, error code, and final state without exposing secrets.

Clients should use unique order references, validate amounts, store provider identifiers, and reconcile callbacks with authoritative API status. It commonly accepts an amount, pricing currency, order reference, callback destination, expiration, description, and payment options, then returns an invoice identifier or hosted payment URL. Providers should document mutability, expiration, retries, and how duplicate requests are handled. Cryptocurrency invoices also require clear rules for exchange rates, network selection, confirmation, underpayment, and late payment. The Invoice API owner should publish stable error semantics and guidance on whether correction, retry, status lookup, or escalation is appropriate.

Testing Invoice API should cover malformed input, denied access, rate limits, timeouts, duplicates, asynchronous completion, and version changes.

Data handled by Invoice API should use documented types, units, timestamp rules, nullable fields, and enum behavior to prevent silent interpretation errors.

The Invoice API contract should define identifiers, validation, authorization, status semantics, errors, limits, and version behavior at the same boundary.

For Invoice API, the application should preserve a correlation path from request construction through response, asynchronous completion, and final business state.