Without webhooks you only see synchronous API responses. Delivery status, retries and receipt run asynchronously — hooks belong in every serious integration.

1. Publish an HTTPS endpoint that can receive JSON (temporary: a tunnel such as ngrok is fine for accp)
2. Register a hook with topic InvoiceSent (send) and/or InvoiceReceived (receive)
3. Respond within 100 seconds with HTTP 2xx
4. Verify the HMAC SHA256 signature before you trust the payload

Exact registration API, headers and retry behaviour: Set up webhooks.

1. Send an invoice (step 5)
2. Receive a hook for the send event
3. Log topic, document/correlation id and verification result
4. Deliberately force a non-2xx to see retries start — then restore 2xx

• Do not put the hook secret in client-side code
• Use separate secrets/URLs for accp and production
• Reject requests with an invalid signature (and log them)

Continue with:

• SDKs and CLI
• Validate API
• API Reference
• Error handling