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Paying Gas in ERC20 Tokens with SDK ⚡️

ERC20 tokens can be used to pay for gas fees. This is achieved through the use of a token paymaster. In this tutorial, we will guide you through the process of sending a user operation using an ERC20 token as the gas payment method.

Set up an owner account

First, we need to set up an Owner for the Smart Account which will be used to sign User Operations (transactions) for the Smart Account.

import { privateKeyToAccount, generatePrivateKey } from "viem/accounts";
 
const privateKey = generatePrivateKey();
const account = privateKeyToAccount(`${privateKey}`);

Set up Nexus client with paymaster

Login to the Dashboard and setup a v2 paymaster. Let's configure a client for the Smart Account with a paymasterUrl to enable it. A bundlerUrl is required to submit transactions to the Network, which will initialize the Smart Account.

import { createSmartAccountClient, createBicoPaymasterClient, toBiconomyTokenPaymasterContext } from "@biconomy/sdk";
import { baseSepolia } from "viem/chains"; 
import { http, parseEther } from "viem";
import { privateKeyToAccount, generatePrivateKey } from "viem/accounts";
 
const privateKey = generatePrivateKey();
const account = privateKeyToAccount(`${privateKey}`);
 
const bundlerUrl = "https://bundler.biconomy.io/api/v3/84532/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44";
const paymasterUrl = "https://paymaster.biconomy.io/api/v2/84532/F7wyL1clz.75a64804-3e97-41fa-ba1e-33e98c2cc703"; 
const baseSepoliaUSDC = "0x036cbd53842c5426634e7929541ec2318f3dcf7e"; 
 
const paymasterContext = toBiconomyTokenPaymasterContext({
    feeTokenAddress: baseSepoliaUSDC
})
 
const nexusClient = await createSmartAccountClient({
    signer: account,
    chain: baseSepolia,
    transport: http(),
    bundlerTransport: http(bundlerUrl),
    paymaster: createBicoPaymasterClient({paymasterUrl}),
    paymasterContext
});

Sending a transaction and paying the gas with USDC

Next, define the transaction you want to send. Use the sendTokenPaymasterUserOp method to send the user operation using the Token Paymaster.

 
import { createSmartAccountClient, createBicoPaymasterClient, toBiconomyTokenPaymasterContext } from "@biconomy/sdk";
import { baseSepolia } from "viem/chains"; 
import { http, parseEther } from "viem";
import { privateKeyToAccount, generatePrivateKey } from "viem/accounts";
 
const privateKey = generatePrivateKey();
const account = privateKeyToAccount(`${privateKey}`);
 
const bundlerUrl = "https://bundler.biconomy.io/api/v3/84532/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44";
const paymasterUrl = "https://paymaster.biconomy.io/api/v2/84532/F7wyL1clz.75a64804-3e97-41fa-ba1e-33e98c2cc703";
const baseSepoliaUSDC = "0x036cbd53842c5426634e7929541ec2318f3dcf7e";
const recipientAddress = "0x0000000000000000000000000000000000000000";
 
const paymasterContext = toBiconomyTokenPaymasterContext({
    feeTokenAddress: baseSepoliaUSDC
})
 
const nexusClient = await createSmartAccountClient({
    signer: account,
    chain: baseSepolia,
    transport: http(),
    bundlerTransport: http(bundlerUrl),
    paymaster: createBicoPaymasterClient({paymasterUrl}),
    paymasterContext
}); 
 
const userOpHash = await nexusClient.sendTokenPaymasterUserOp({
    calls: [
        {
            to: recipientAddress,
            value: 1n,
            data: "0x"
        }
    ],
    feeTokenAddress: baseSepoliaUSDC
})
 
const receipt = await nexusClient.waitForUserOperationReceipt({ hash: userOpHash })

For a complete list of supported ERC20 tokens that can be used for gas payment, check out our supported tokens documentation.

By following these steps, you have successfully sent a transaction and paid the gas with USDC token using the SDK. For more advanced features and options, refer to the official documentation.

See sendTransaction Docs