Gasless Payment

Users can pay with just a signature — no gas fees required.

Overview

Gasless payments use the ERC-2771 meta-transaction standard. Users can pay with ERC-20 tokens without needing native tokens (MATIC, ETH, etc.) for gas.

Use Cases

• New user onboarding (first payment without gas)
• Better UX (pay with just a signature)
• Eliminate gas fee volatility

Regular vs. Gasless Payment

Regular Payment                    Gasless Payment
──────────────                     ──────────────────

  User                               User
    │                                  │
    │ Send TX                          │ Sign only
    │ (pay gas)                        │ (no gas)
    ▼                                  ▼
  Contract                          Relayer
                                        │
                                        │ Send TX
                                        │ (pay gas)
                                        ▼
                                    Contract

Components

1. EIP-712 Signature

A typed signature created by the user's wallet.

• Domain, types, and message are clearly displayed
• User can verify signature content
• Replay attack prevention (nonce, deadline)

2. ERC2771 Forwarder

OpenZeppelin's ERC2771Forwarder contract.

• Signature verification
• Restores original sender (_msgSender())
• Forwards calls to PaymentGateway

3. Relayer

Converts signed requests into on-chain transactions.

• Validates signature format
• Pays gas fees
• Submits and monitors transactions

Relay Status Flow

QUEUED ────▶ SUBMITTED ────▶ CONFIRMED
                │
                ▼
              FAILED

Status	Description
QUEUED	Relay request queued
SUBMITTED	Transaction submitted
CONFIRMED	Transaction confirmed
FAILED	Transaction failed

Limitations

• Token must be approved for the PaymentGateway contract in advance
• A Relayer service must be configured for the chain
• forwarderAddress is included in the payment creation response (if missing, Gasless is not supported)

Supported Chains

Chain	Network ID
Polygon Amoy	80002
BSC Testnet	97
Sepolia	11155111

Next Steps

• Implementation Guide - Detailed implementation guide