API reference - Invoice-AI API

These pages are generated from the OpenAPI 3.1 document at /api/v1/openapi.json.

https://invoice.horizonpay.co/api/v1

Authenticate with Authorization: Bearer inv_live_.... In each endpoint’s playground, paste your key into the Authorization field.

The playground calls the live API. Writes create real records, and send emails real people. Use a short-lived key and a customer whose email you control.

Prefer Postman? Fork the whole collection in one click.

Conventions

Topic	Rule
Money & IDs	Integer minor units (`150000` is 1,500.00). `cus_`, `prod_`, `price_`, `in_`, `ii_` id prefixes.
Errors	`application/problem+json`. Branch on `code`.
Idempotency	Required on invoice creation and lifecycle actions.
Pagination	Cursor-based, `limit` up to 100.
Rate limits	120 requests per minute per key. 10 sends per hour per key, 50 per account.

Versioning

The major version is in the path (/v1). New endpoints and fields can ship within v1, so ignore fields you don’t recognise. Breaking changes ship under a new major version. See the changelog.