Permit2 Approval

Before the first Permit2 payment on a given wallet/token/chain combination, the payer wallet must grant the Permit2 contract an ERC-20 allowance. This is a one-time transaction — once done, it does not need to be repeated for the same wallet/token/chain.

Why This Is Needed

Permit2 works by having the Permit2 contract pull tokens from the payer's wallet on behalf of a spender (the Ivorypay gas-payer vault). For this to succeed, the token contract must allow the Permit2 contract to move funds. Without this allowance, the on-chain transfer will revert and the deposit will fail with:

x402: insufficient Permit2 allowance — sender must approve Permit2 contract

Permit2 Contract Address

The Permit2 contract is deployed at the same address on every EVM chain:

0x000000000022D473030F116dDEE9F6B43aC78BA3

When You Need It

See Supported Assets. Permit2 is used for:

• Any transfer on BSC or Ethereum (any token).

• Any non-USDC token on any chain.

EIP-3009 transfers (USDC on Base, Polygon, Lisk) do not require this approval.

Checking Existing Allowance

Before sending an approval transaction, check whether the allowance is already sufficient:

import { ethers } from 'ethers';

const PERMIT2_ADDRESS = '0x000000000022D473030F116dDEE9F6B43aC78BA3';

const provider     = new ethers.JsonRpcProvider(YOUR_RPC_URL);
const erc20        = new ethers.Contract(TOKEN_ADDRESS, [
  'function allowance(address owner, address spender) view returns (uint256)',
  'function approve(address spender, uint256 amount) returns (bool)',
], provider);

const allowance = await erc20.allowance(WALLET_ADDRESS, PERMIT2_ADDRESS);

if (allowance >= ethers.MaxUint256 / 2n) {
  console.log('Already approved — no action needed.');
} else {
  console.log('Approval required.');
}

Running the Approval

The approval transaction requires a funded wallet with native gas tokens (BNB on BSC, ETH on Ethereum). Connect the wallet to a provider for the correct chain:

import { ethers } from 'ethers';
import 'dotenv/config';

const PERMIT2_ADDRESS = '0x000000000022D473030F116dDEE9F6B43aC78BA3';

// Replace with your chain's RPC URL and the token address you want to approve
const RPC_URL      = process.env.RPC_BSC_MAINNET_URL;  // e.g. BSC mainnet
const TOKEN_ADDRESS = '0x55d398326f99059fF775485246999027B3197955'; // USDT on BSC

const provider = new ethers.JsonRpcProvider(RPC_URL);
const wallet   = new ethers.Wallet(process.env.EVM_PRIVATE_KEY, provider);

const erc20 = new ethers.Contract(TOKEN_ADDRESS, [
  'function allowance(address owner, address spender) view returns (uint256)',
  'function approve(address spender, uint256 amount) returns (bool)',
], wallet);

async function approvePermit2() {
  const current = await erc20.allowance(wallet.address, PERMIT2_ADDRESS);

  if (current >= ethers.MaxUint256 / 2n) {
    console.log('Already approved (max allowance). No action needed.');
    return;
  }

  console.log('Approving Permit2 for MaxUint256…');
  const tx = await erc20.approve(PERMIT2_ADDRESS, ethers.MaxUint256);
  console.log('Tx hash:', tx.hash);
  await tx.wait();
  console.log('Approval confirmed.');
}

approvePermit2().catch(console.error);

Notes

• The approval amount is MaxUint256 (unlimited). This avoids re-approving as the balance is spent.

• The approval is scoped to the Permit2 contract only — not to Ivorypay directly. Permit2 then enforces per-transfer limits through the signed authorization.

• If you rotate the payer wallet address, the new wallet must complete its own approval.

• The approval does not expire on-chain. It remains valid until explicitly revoked or replaced.