> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.trygrant.com/introduction/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.trygrant.com/_mcp/server.

# Introduction

Grant is a billing platform that helps you meter usage, manage customers and subscriptions, and generate invoices. The Grant API gives you programmatic access to every part of the billing lifecycle.

## Core concepts

| Concept           | Description                                                                                                                                                                                 |
| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Customers**     | The people or organizations you bill. Each customer can have billing and shipping addresses, an external ID for mapping to your system, and one or more subscriptions.                      |
| **Subscriptions** | Link a customer to a plan. Subscriptions track status, billing anchor day, and renewal dates.                                                                                               |
| **Invoices**      | Itemized bills sent to customers. Invoices follow a lifecycle from `draft` to `open` to `paid` (or `void` / `uncollectible`). Line items can be added, updated, and removed while in draft. |
| **Events**        | Billable usage events you send to Grant. Events are identified by an idempotency key and processed asynchronously via a durable queue.                                                      |

## How it works

#### Send usage events

Instrument your application to send billable events to the `/v1/events/ingest` endpoint whenever metered activity occurs (API calls, compute time, storage, etc.).

#### Manage customers and subscriptions

Create customers and attach them to plans via subscriptions. Grant tracks billing periods and renewal dates automatically.

#### Generate invoices

Create draft invoices, add line items, and finalize them to assign an invoice number and open them for payment. Grant provides a hosted payment page for each finalized invoice.

## API design

The Grant API follows these conventions:

* **Base URL** — `https://api.trygrant.com`
* **Authentication** — Bearer token via API key (see [Authentication](/api-reference/authentication))
* **Content type** — All request and response bodies are `application/json`
* **Pagination** — List endpoints use cursor-based pagination with `limit` and `cursor` query parameters
* **Error format** — Errors return `{ success: false, error: { code, message }, request_id }`
* **Rate limiting** — 1,000 requests per minute per company. Rate limit headers (`X-RateLimit-Limit`, `X-RateLimit-Remaining`, `X-RateLimit-Reset`) are included on every response.

## Next steps

#### [Quickstart](/quickstart)

Send your first event and create an invoice in under 5 minutes

#### [Authentication](/api-reference/authentication)

Learn how to authenticate your API requests

#### [API reference](/api-reference)

Browse the full API reference with interactive examples

> API documentation for Grant — billing infrastructure for usage-based pricing