How stablecoin payments work

Most explanations of crypto payments start with what a blockchain is. This one starts at the checkout, because that is where you actually are.

What happens when you press “pay with USDC”

1. The merchant asks a gateway for an invoice. Almost no merchant handles this themselves. They use a payment gateway — Coinbase Commerce, BitPay, NOWPayments, Stripe and others — which does the chain-watching work.

2. The gateway quotes you an amount and an address. You see the stablecoin amount, a destination address, usually a QR code, a network name, and a countdown. Because stablecoins are dollar-denominated, a $49 invoice is 49 USDC — there is no exchange rate to worry about, unlike paying in a volatile asset.

3. The countdown is a price lock. It exists mainly for volatile assets, where the quote would otherwise drift. For stablecoins it is mostly a housekeeping window: the gateway will not watch an address forever. Ten to fifteen minutes is typical.

4. You send the transfer. From your wallet or an exchange account. This is the step where the network you select matters, and where mistakes are permanent.

5. The gateway sees it and counts confirmations. Your transaction enters the network, gets included in a block, and the gateway watches. It waits for a set number of confirmations before treating the payment as settled — a risk decision the gateway makes, not a rule of the protocol.

6. The merchant releases the order. The gateway tells the merchant’s system the invoice is paid. The download unlocks, the licence key sends, the booking issues.

On Solana or Base this whole sequence takes seconds. On Ethereum mainnet it takes a few minutes.

The pieces worth understanding

The network is not a preference, it is an address space

USDC on Ethereum, USDC on Base and USDC on Solana are three different tokens on three different networks. They are worth the same and issued by the same company, and they are not interchangeable in a transfer.

Sending to a correct address on the wrong network is the most common expensive mistake in crypto payments. Sometimes the funds land at an address the merchant also controls on that chain and can be recovered through support. Often they do not.

The safeguard is trivial: read the network name at checkout, select the same one in your wallet, and for a large payment send a small test first.

Gas is paid in the chain’s own token

Moving USDC costs a network fee, and that fee is paid in ETH, SOL, POL or TRX depending on the chain — never in the token you are sending.

This catches people constantly. A wallet shows $500 of USDC and refuses to send any of it, because there is no ETH to pay the fee. Keep a small balance of the native token in any wallet you pay from.

Confirmations are a risk judgement

A gateway waiting for three confirmations rather than one is deciding how much reorganisation risk it will accept. On networks with fast deterministic finality — Avalanche, Solana, Stellar — there is essentially nothing to wait for, which is why those checkouts feel instant.

The gateway is doing more than watching

It converts if the merchant wants fiat, it handles underpayments and overpayments, it produces the accounting record, and it decides which coins and networks the merchant can offer. That last point is why the answer to “which coins does this shop take?” is usually “whatever its gateway supports.”

Custodial and non-custodial gateways

Worth knowing because it affects who holds your money in transit.

Custodial gateways receive the payment themselves, convert if needed, and settle to the merchant — often in fiat to a bank account. BitPay and Stripe work this way. The merchant never touches crypto, which is precisely why they chose it.

Non-custodial gateways route the payment straight to the merchant’s own wallet and never take possession. NOWPayments is the common example. The merchant receives stablecoins and handles whatever comes next.

From your side the checkout looks identical. It matters for the merchant’s risk and, occasionally, for how a refund can be handled.

Refunds, and why they are the weak point

There is no reversal mechanism. A refund is a new payment the merchant chooses to send, to an address you supply, at a time they decide.

That has three consequences worth planning around. It is slower than a card refund — manual rather than automated. It requires you to give a correct address, and an error there is your problem. And it depends entirely on the merchant’s willingness, because no payment network will compel it.

Reputable merchants handle refunds properly. The point is that the system does not make them, which is a meaningful difference from cards and the main reason to think twice before paying a large sum to an unfamiliar merchant on-chain.

What can go wrong, and what to do

Underpayment. You sent slightly less than invoiced, often because your wallet deducted a fee from the amount. Most gateways flag it and let you top up. Send the exact invoiced amount.

Late payment. Arrived after the window closed. Usually re-quoted automatically. Keep the transaction hash.

Wrong network. Contact the merchant immediately with the transaction hash. Recovery depends on whether they control the destination address on that chain.

Payment confirmed but order not released. Uncommon, and the transaction hash resolves it in one support message. Always keep it.

The rule that covers most of this

Read the checkout page. It states the coin, the amount, the network and the deadline. Nearly every expensive mistake in stablecoin payments is a case of one of those four being different from what the payer assumed.

Next: which network to pay on, or where to spend stablecoins.