# Getting Started

The Lunch Partner API lets your platform offer government vendors early payment on their invoices.
Lunch advances funds to the vendor. The city pays the invoice on its normal schedule, Lunch recovers
the advance and fees from that payment, and the remainder goes to the vendor.

The API accepts JSON request bodies (CSV for invoice imports), returns JSON, and uses standard HTTP
verbs and status codes. Requests authenticate with a bearer token. All API keys are live. See
[Authentication](/authentication).

## Key Terms

| Term | Description |
| --- | --- |
| Payee | The organization owed the money, typically the vendor. |
| Payor | The organization that owes the money, typically a city or agency. |
| Face value | The invoice's full amount. |
| Advance | The amount Lunch pays the payee up front. |
| Fees | The cost of the advance. Deducted from the payor's payment, not the advance. |
| Organization | A payee or payor. Error codes use "business," for example `business_not_found`. |

## Core Calls

| Action | Call |
| --- | --- |
| Sync an organization | `PUT /v1/organizations/{externalId}` |
| Sync an invoice | `PUT /v1/invoices/{externalId}` |
| Quote an advance | `POST /v1/quotes` |
| Request an advance | `POST /v1/advances` |

Vendors must complete [onboarding](/onboarding) before receiving an advance.

## Conventions

| Convention | Detail |
| --- | --- |
| Identifiers | Your own `externalId`. No Lunch identifiers to store. See [External IDs](/external-ids). |
| Idempotency | Writes keyed on your identifier are safe to retry. See [Idempotent Requests](/idempotent-requests). |
| Amounts | Integer cents. `100000` is $1,000.00. |
| Invoice dates | ISO date-times. |
| Errors | `{ error, code }`. See [Errors](/errors). |

## What's Next

- [Quickstart](/quickstart): request a first advance in seven steps.
- [Requesting an Advance](/financing-an-invoice): the full sequence of calls.
- [API reference](/reference): every operation.