How a crypto payment gateway works, from invoice to settlement

A wallet stores keys. An exchange trades assets. A payment gateway sits between your checkout and the blockchain: it creates a payment request, watches the chain for the customer's transfer, decides when it counts as paid, tells your backend, and gets the funds to where you can use them.

The hard parts are operational rather than cryptographic — watching several networks reliably, handling partial, late and duplicate payments, and keeping a ledger that always matches the chain. That is what you buy instead of building.

1. 01Create an invoice. Your backend asks the gateway for a payment of, say, 49.99 USD in USDT on Tron. The gateway converts it, locks the rate and returns a deposit address that belongs to this invoice alone.
2. 02Show the customer the address. Your checkout displays the address and amount, usually as text plus a QR code, with a countdown to expiry.
3. 03The customer pays. They send the asset from any wallet or exchange. The gateway's chain listener sees the transaction and the invoice moves from pending to detected.
4. 04Wait for confirmations. One block isn't proof of payment; the invoice sits in confirming until the network's required number of confirmations is reached. See crypto payment confirmations.
5. 05Confirm and notify. The invoice becomes confirmed, the merchant's ledger is credited and a signed webhook tells your backend to release the order.
6. 06Settle and withdraw. The deposit is swept from the one-time address to the merchant's wallet (forwarding, then settled), after which the balance can be withdrawn to any address.

With one address per invoice, the gateway can attribute an incoming transfer to an order without asking the customer to paste a memo or transaction hash. The amount, the network and the address together identify the payment, which is also what makes underpayments and late payments detectable rather than ambiguous.

That depends on the provider. Payaries holds the funds for you: each merchant has a dedicated wallet per chain — never pooled with other merchants — and the on-chain balance can be checked against a block explorer. The trade-offs are covered in managed vs self-held payment gateways.

For a developer it is three pieces: a server call to create the invoice, a checkout that displays the address, and a webhook endpoint that marks the order paid. The crypto payment API page shows each with real requests.