> ## Documentation Index
> Fetch the complete documentation index at: https://docs.horizonpay.co/llms.txt
> Use this file to discover all available pages before exploring further.

# API reference

> Every Invoice-AI v1 endpoint, generated from the live OpenAPI document.

These pages are generated from the OpenAPI 3.1 document at [`/api/v1/openapi.json`](https://invoice.horizonpay.co/api/v1/openapi.json).

```text theme={null}
https://invoice.horizonpay.co/api/v1
```

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

<Warning>
  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.
</Warning>

Prefer Postman? [Fork the whole collection](/postman) in one click.

## Conventions

| Topic | Rule |
| - | - |
| [Money & IDs](/money-and-ids) | Integer minor units (`150000` is 1,500.00). `cus_`, `prod_`, `price_`, `in_`, `ii_` id prefixes. |
| [Errors](/errors) | `application/problem+json`. Branch on `code`. |
| [Idempotency](/idempotency) | Required on invoice creation and lifecycle actions. |
| [Pagination](/pagination) | Cursor-based, `limit` up to 100. |
| [Rate limits](/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](/changelog).


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