# Lunch Partner API

Your vendors get paid when their invoice is financed instead of when it is due. You keep the
relationship; Lunch carries the money and the risk.

The whole integration is four calls:

| | |
| --- | --- |
| **Sync a business** | `PUT /v1/organizations/{externalId}` — with your own identifier for it |
| **Sync an invoice** | `PUT /v1/invoices/{externalId}` — payee, payor, face value, dates |
| **Quote** | `POST /v1/quotes` — what a face value would cost, naming no invoice |
| **Advance** | `POST /v1/advances` — take it against a synced invoice |

Everything is keyed on **your** identifiers. You never store a Lunch id, and each of these writes
is idempotent on the identifier you send, so replaying your ledger updates rather than duplicates.
([Subscribing to a webhook destination is the one exception.](/errors))

## Before a business can borrow

Three gates, independent of each other, all reported by
[`GET /v1/organizations/{externalId}`](/reference#get-/v1/organizations/-externalid-):

- **Compliance** — we hold a tax identification number and it has cleared.
- **An agreement** — somebody at the business has signed it.
- **A bank account** — we know where the money goes.

Today, get a business through them by inviting it: set the payout account yourself with
[`PUT /v1/organizations/{externalId}/payout-account`](/reference#put-/v1/organizations/-externalid-/payout-account)
when you already hold the vendor's bank details, and send them
[`POST /v1/invitations`](/reference#post-/v1/invitations) to claim the account and sign.

<Callout type="note" title="Hosted onboarding is published but not yet live">
[`POST /v1/onboarding-sessions`](/reference#post-/v1/onboarding-sessions) mints a single-use link
that collects all three gates over your own page, without the vendor leaving your product. Its
shape is published so an integration can be written against it now — **a link minted today
resolves to nothing.** We will tell you when it is serving.
</Callout>

## Where to go next

- [Authentication](/authentication) — your key, and what the playground on this site does with it
- [Financing an invoice](/financing-an-invoice) — the four calls end to end
- [Webhooks](/webhooks) — events, signatures, and verifying one
- [Errors](/errors) — the shape every failure takes, and the codes to branch on
- [API reference](/reference) — every operation, generated from the contract itself