Create your first payment

Who this is for

Developers connecting an existing order-management system to Outpay for the first time.

Before you begin

An API key with the checkouts:create scope.
An internal order ID you can pass through as metadata and use as an idempotency key.

Steps

Generate an API key with checkouts:create and keep it server-side.

Create one checkout with the order ID in metadata.orderId and a stable Idempotency-Key.

Persist the returned checkout ID, payment URL, amount, and expiry alongside your order.

Redirect the customer to paymentUrl.

Wait for checkout.paid, after verifying its signature.

Fulfil the order exactly once, using a unique order-state transition.

Expected result

The customer pays Base USDC directly to the merchant's wallet, and your server can reconcile the order from the checkout reference and transaction hash alone.

Common problems

Problem	Likely cause	Next step
Checkout creation returns `409`	An idempotency key was reused with a different order payload, or the merchant is inactive.	See errors for the exact code and required action.
No webhook ever arrives	No webhook endpoint is configured yet.	Configure one from Developers before relying on webhooks; poll as a fallback in the meantime.

Quickstart — the same flow with full request/response examples.
Receive and process webhooks — the fulfilment step in detail.
Idempotency — safely retrying the create-checkout call.