> ## Documentation Index
> Fetch the complete documentation index at: https://docs.eco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Gasless USDC deposits into Circle Gateway

> Have a user deposit USDC into Circle Gateway on Polygon without holding source-chain gas, they sign an ERC-3009 authorization; Eco broadcasts. Settled in 20–40 seconds.

This recipe walks through the cleanest gasless funding path Eco supports today: a user signs an ERC-3009 `transferWithAuthorization`; Eco's relayer broadcasts; USDC lands in the user's Circle Gateway balance on Polygon.

## When to use

* Onboarding flows where users don't yet hold the source chain's gas token
* Nanopayment / micro-deposit flows where gas would dominate the value transferred
* Any flow where the UX win of "no gas" beats the marginal latency

## 1. Create the quoted deposit vault

```bash theme={null}
curl -X POST https://api.eco.com/circle-gateway/v2/depositAddresses \
  -H "Content-Type: application/json" \
  -d '{
    "sourceChainId": 8453,
    "amount": "100000000",
    "recipient": "0xRecipientOnGateway",
    "depositor": "0xUserWallet"
  }'
```

Returns `{ vaultAddress, amount, deadline }`. The vault is quoted for this specific `amount`; fund it before `deadline` (Unix seconds). Repeating the same request while the quote is pending returns the same vault.

## 2. Have the user sign an ERC-3009 authorization

Sign for the quoted `amount`, with `to` set to the `vaultAddress`. USDC's EIP-712 domain `name` varies per chain: `"USDC"` on Base Sepolia, `"USD Coin"` elsewhere. Use the right one.

```typescript theme={null}
import { toHex } from 'viem';

const value = BigInt(amount); // quoted amount from step 1
const nonce = toHex(crypto.getRandomValues(new Uint8Array(32)));
const validBefore = String(Math.floor(Date.now() / 1000) + 3600);

const signature = await signTypedDataAsync({
  domain: { name: 'USD Coin', version: '2', chainId, verifyingContract: USDC_ADDRESS },
  types: {
    TransferWithAuthorization: [
      { name: 'from', type: 'address' },
      { name: 'to', type: 'address' },
      { name: 'value', type: 'uint256' },
      { name: 'validAfter', type: 'uint256' },
      { name: 'validBefore', type: 'uint256' },
      { name: 'nonce', type: 'bytes32' },
    ],
  },
  primaryType: 'TransferWithAuthorization',
  message: { from: owner, to: vaultAddress, value, validAfter: 0n, validBefore: BigInt(validBefore), nonce },
});
```

## 3. Submit the signed authorization

```bash theme={null}
curl -X POST https://api.eco.com/circle-gateway/v1/gasless/transferWithAuthorization \
  -H "Content-Type: application/json" \
  -d '{
    "chainId": 8453,
    "from": "0xSigner",
    "to": "0xVaultAddress",
    "value": "100000000",
    "validAfter": "0",
    "validBefore": "1717200000",
    "nonce": "0x...",
    "signature": "0x..."
  }'
```

Returns `202 Accepted` with `{ id, status: "PENDING" }`. The `value` must be at least the quoted `amount` and the vault's quote must not be expired.

## 4. Poll for completion

Poll the relayer job:

```bash theme={null}
curl https://api.eco.com/circle-gateway/v1/gasless/jobs/<id>
```

Status transitions: `PENDING` → `COMPLETED` (or `FAILED`). Response includes `transferTxHash` once complete.

Then poll the vault status until the deposit intent is published:

```bash theme={null}
curl "https://api.eco.com/circle-gateway/v2/depositAddresses/0xVaultAddress?sourceChainId=8453"
```

`state` transitions `PENDING` → `FUNDING_DETECTED` → `PUBLISHED`, and the response carries the `intentHash`. See the [state table](/addresses/gateway-fast-deposits#step-3-poll-for-completion) for the full list.

End-to-end (Base Sepolia → Polygon Amoy): typically **20–40 seconds**.

## What the user paid

Nothing onchain. Eco's deposit-address service paid source-chain gas; Eco's solver service paid Polygon-side gas.

You've successfully completed a gasless deposit into Gateway.