ERC20 Deposit and Withdraw Guide

High Level Flow

Deposit ERC20 (2 step process)

  1. The tokens need to be first approved to the Polygon rootchain contract on Parent Chain (Ethereum/Goerli).
  2. Once approved, the deposit function is to be invoked where the tokens get deposited to the Polygon contract, and are available for use in Polygon.

Transfer ERC20

Once you have funds on Polygon, you can use those funds to send to others instantly.

Withdraw ERC20 (3 step process)

  1. Withdrawal of funds is initiated from Polygon. A checkpoint interval of 30 mins(For testnets wait for ~10 minutes) is set, where all the blocks on the Polygon block layer are validated since the last checkpoint.
  2. Once the checkpoint is submitted to the mainchain ERC20 contract, an NFT Exit (ERC721) token is created of equivalent value. Users need to wait for a about 2 seconds challenge period (For testnets also)
  3. Once the challenge period is complete, the withdrawn funds can be claimed back to your ERC20 acccount from the mainchain contract using a process-exit procedure.

For now, just go with the fact that the challenge period for withdrawals is an important part of the Plasma framework to ensure security of your transactions. Later, once you get to know the system better, the reason for the 7-day withdrawal window will become clear to you.

Setup Details

Configuring Polygon SDK

Install Matic SDK (2.0.2)

npm install --save @maticnetwork/maticjs


Initiating Maticjs client

const bn = require("bn.js");
const HDWalletProvider = require("@truffle/hdwallet-provider");
const Network = require("@maticnetwork/meta/network");
const Matic = require("@maticnetwork/maticjs").default;
const SCALING_FACTOR = new bn(10).pow(new bn(18));
async function getMaticClient(_network = "testnet", _version = "mumbai") {
const network = new Network(_network, _version);
const { from } = getAccount();
const matic = new Matic({
network: _network,
version: _version,
parentProvider: new HDWalletProvider(
maticProvider: new HDWalletProvider(
parentDefaultOptions: { from },
maticDefaultOptions: { from },
await matic.initialize();
return { matic, network };
function getAccount() {
if (!process.env.PRIVATE_KEY || !process.env.FROM) {
throw new Error("Please set the PRIVATE_KEY/FROM env vars");
return { privateKey: process.env.PRIVATE_KEY, from: process.env.FROM };
module.exports = {


Create a new file in root directory name it process.env

FROM = ""


Approve: This is a normal ERC20 approval so that depositManagerContract can call transferFrom function. Polygon Plasma client exposes approveERC20TokensForDeposit method to make this call.

deposit: Deposit can be done by calling depositERC20ForUser on depositManagerContract contract.

Note that token needs to be mapped and approved for transfer beforehand.

depositERC20ForUser method to make this call.

const utils = require('./utils')
async function execute() {
const { matic, network } = await utils.getMaticClient()
const { from } = utils.getAccount()
const token = network.Main.Contracts.Tokens.TestToken
const amount = matic.web3Client.web3.utils.toWei('1.567')
// approve
await matic.approveERC20TokensForDeposit(token, amount).then((res) => {
console.log("approve hash: ", res.transactionHash)
// deposit
await matic.depositERC20ForUser(token, from, amount)).then((res) => {
console.log("deposit hash: ", res.transactionHash)
execute().then(_ => process.exit(0))

NOTE: Deposits from Ethereum to Polygon happen using a state sync mechanism and takes about ~5-7 minutes. After waiting for this time interval, it is recommended to check the balance using web3.js/matic.js library or using Metamask. The explorer will show the balance only if at least one asset transfer has happened on the child chain. This link explains how to track the deposit events.


recipient is the receiver’s address, to whom the funds are supposed to be sent.

const utils = require("./utils");
async function execute() {
const { matic, network } = await utils.getMaticClient();
const { from } = utils.getAccount();
const recipient = "<>";
const childTokenAddress = network.Matic.Contracts.Tokens.TestToken;
const amount = matic.web3Client.web3.utils.toWei("1.23");
await matic
.transferERC20Tokens(childTokenAddress, recipient, amount, {
parent: false,
.then((res) => {
console.log("Transfer hash: ", res.transactionHash);
execute().then((_) => process.exit(0));


1. Burn

User can call withdraw function of getERC20TokenContract child token contract. This function should burn the tokens. Polygon Plasma client exposes startWithdraw method to make this call.

const utils = require("./utils");
async function execute() {
const { matic, network } = await utils.getMaticClient();
const { from } = utils.getAccount();
const token = network.Matic.Contracts.Tokens.TestToken;
const amount = matic.web3Client.web3.utils.toWei("5.678");
await matic.startWithdraw(token, amount, { from }).then((res) => {
console.log("Burn hash: ", res.transactionHash);
execute().then((_) => process.exit(0));

2. confirm-withdraw.js

User can call startExitWithBurntTokens function of erc20Predicate contract. This function should burn the tokens. Polygon Plasma client exposes withdraw method to make this call. This function can be called only after the checkpoint is included in the main chain. The checkpoint inclusion can be tracked by following this guide.

//Wait for ~10 mins for Mumbai testnet or ~30mins for Ethereum Mainnet till the checkpoint is submitted for burned transaction, then run the confirm withdraw
const utils = require("./utils");
async function execute() {
const { matic } = await utils.getMaticClient();
const { from } = utils.getAccount();
// Submit proof of burn on Main Chain
const txHash = "<>";
await matic.withdraw(txHash, { from, gas: "7000000" }).then((res) => {
console.log("Confirm withdraw hash: ", res.transactionHash);
// Withdraw process is completed, funds will be transfered to your account after challege period is over.
execute().then((_) => process.exit(0));

3. Process Exit

Once the Challenge Period has been passed for the transaction present in checkpoint, user should call the processExits function of withdrawManager contract and submit the proof of burn. Upon submitting valid proof tokens are transferred to the user. Polygon Plasma client exposes processExits method to make this call.

const utils = require("./utils");
async function execute() {
const { matic, network } = await utils.getMaticClient();
const { from } = utils.getAccount();
const token = network.Main.Contracts.Tokens.TestToken;
await matic.processExits(token, { from, gas: 7000000 }).then((res) => {
console.log("Exit hash: ", res.transactionHash);
execute().then((_) => process.exit(0));

Note: A checkpoint, which is a representation of all transactions happening on the Polygon Network to the ERC20 chain every ~30 minutes, is submitted to the mainchain ERC20 contract.

Note: Once the checkpoint is submitted, user needs to wait for a challenge period of 2 seconds.

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