# Invoice payment sequence

Invoice payment sequence.

<figure><img src="https://files.cryptopay.me/b2b/git_book_files/08_Invoice_Invoice_Payment_Sequence.svg" alt=""><figcaption></figcaption></figure>

Once an invoice is created, we start monitoring its cryptocurrency address to detect inbound transactions.

1. The customer specifies a purchase amount and purchase currency (if necessary)
2. The merchant makes an API call `POST /api/invoices` to [create an invoice](https://reference.cryptopay.me/#tag/Invoices/operation/invoices.create)
3. Cryptopay responds with the invoice details
4. The merchant displays the payment details to the customer (a destination wallet address, an exact amount to send, a QR code etc)
5. The customer broadcasts a cryptocurrency transaction
6. Cryptopay sends the 1st callback to notify the merchant about the fact that the customer has just broadcast their transaction
7. Cryptopay is waiting for the transaction to be confirmed on the network
8. Cryptopay sends the 2nd callback to notify the merchant about the fact that the transaction has been confirmed
9. Cryptopay changes the invoice status from `new` to `completed` and sends the final callback
10. The merchant makes an API call `GET /api/invoices/:id` to retrieve the invoice status
11. The invoice status is returned
12. The merchant marks the payment as successful on their side