;
};
Request and settle a payment in one wallet interaction. A direct USDC transfer works with any EIP-1193 wallet, while B20 adds issuer-defined policy controls and an onchain order memo.
This is the auto-settle path: the wallet approval and token transfer happen in one flow. If you need to approve now and settle later, [authorize a payment](/build-on-base/accept-payments/authorize-a-payment) instead.
#### Demo
The demo above is mock only. If you want to see onchain demos on Vibenet, head to [Base chain demos](https://chain.base.org/demos).
| Rail | Best for | Integration |
| ------------- | ---------------------------------------- | ---------------- |
| Direct USDC | Wallet-agnostic ERC-20 checkout | viem |
| B20 with memo | Issuer tokens and onchain reconciliation | viem or Solidity |
## Accept a Wallet-Native USDC Transfer
Base Sepolia USDC is `0x036CbD53842c5426634e7929541eC2318f3dCF7c`; Base mainnet USDC is `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`.
Testnet deployments can be reset. Confirm `eth_getCode` returns contract bytecode at the configured USDC address and that your faucet issued the same asset before asking a user to sign.
```typescript TypeScript lines wrap expandable highlight={3,10} theme={null}
export async function sendUsdc(merchant: Address) {
const { account, publicClient, walletClient } = await browserClients();
const simulation = await publicClient.simulateContract({
account,
address: USDC,
abi: erc20Abi,
functionName: "transfer",
args: [merchant, parseUnits("5", 6)],
});
const hash = await walletClient.writeContract(simulation.request);
const receipt = await publicClient.waitForTransactionReceipt({ hash });
if (receipt.status !== "success") throw new Error("USDC transfer reverted");
return hash;
}
```
The receipt succeeds and the standard USDC `Transfer` event records the merchant and amount.
## Accept B20 with a Memo
A direct wallet can call `transferWithMemo`. A checkout contract can instead pull an approved amount with `transferFromWithMemo` and reject duplicate order IDs.
The demo above is mock only. If you want to see onchain demos on Vibenet, head to [Base chain demos](https://chain.base.org/demos).
```typescript TypeScript lines wrap expandable highlight={4,8,11} theme={null}
export async function sendB20WithMemo(token: Address, merchant: Address) {
const { account, publicClient, walletClient } = await browserClients();
const memo = stringToHex("order-8842", { size: 32 });
const simulation = await publicClient.simulateContract({
account,
address: token,
abi: b20PaymentAbi,
functionName: "transferWithMemo",
args: [merchant, parseUnits("25", 6), memo],
});
const hash = await walletClient.writeContract(simulation.request);
const receipt = await publicClient.waitForTransactionReceipt({ hash });
const events = parseEventLogs({ abi: b20PaymentAbi, logs: receipt.logs, strict: true });
if (events[0]?.eventName !== "Transfer" || events[1]?.eventName !== "Memo") {
throw new Error("Expected adjacent Transfer and Memo events");
}
return hash;
}
```
```solidity Solidity lines wrap expandable highlight={4} theme={null}
function pay(bytes32 orderId, uint256 amount) external {
if (paid[orderId]) revert OrderAlreadyPaid(orderId);
paid[orderId] = true;
bool transferred = token.transferFromWithMemo(msg.sender, merchant, amount, orderId);
require(transferred, "B20 transfer failed");
}
```
If the Solidity checkout calls `transferFromWithMemo`, the payer must approve it and any `TRANSFER_EXECUTOR_POLICY` must authorize the checkout contract. The merchant must still verify the expected amount before fulfillment.
See the [B20 token standard](/base-chain/network-information/b20-token-standard) for the complete B20 interface and memo details.
## Verify Before Fulfillment
A successful wallet prompt is not a fulfillment signal. Verify the recipient, token, sender, amount, memo when present, and replay state on your backend.
Validate settlement and claim each transaction hash exactly once.
## See Also
Separate wallet approval from merchant-controlled capture.
Confirm settlement server-side before you ship.