# SettlementContract reference

> ABI, storage layout, and deployment addresses for SettlementContract.sol.

The `SettlementContract` is the on-chain endpoint of every `aa-native` payment. This page is the contract's reference card. The conceptual overview is on the [Settlement contract concept page](/docs/core-concepts/settlement-contract).

## Deployment addresses

| Network | Proxy | Implementation |
|---|---|---|
| NERO mainnet (`eip155:1689`) | `0x5eCfc64f2339992668f555918674B604F97B412D` | `0xb7f16185619c476ce3fd3fd9e8b6186e340802f6` |
| NERO testnet (`eip155:689`) | `0x925dbba44570683ac8da99be08bc5ece8cf5a8c6` | (proxy implementation address) |

The proxy is the address callers reference. Implementation addresses change on upgrade.

## Public interface

### `settle(address merchant, address token, uint256 amount, bytes32 requestHash)`

Settles one payment. Reverts on:

| Condition | Custom error |
|---|---|
| `msg.value != 0` | `UnexpectedNativeValue()` |
| `merchant == address(0)` | `ZeroAddress()` |
| `token == address(0)` | `ZeroAddress()` |
| `amount == 0` | `ZeroAmount()` |
| `requestHash == bytes32(0)` | `ZeroRequestHash()` |
| `!isTokenAllowed[token]` | `TokenNotAllowed(address token)` |
| `isSettled[requestHash]` | `AlreadySettled(bytes32 requestHash)` |
| Reentrancy guard tripped | (`ReentrancyGuardReentrantCall()`) |
| Contract is paused | (`EnforcedPause()`) |

After validation, `isSettled[requestHash]` is set to `true`, then `IERC20(token).safeTransferFrom(msg.sender, merchant, amount)` runs. The contract post-checks that the merchant's balance increased by exactly `amount`. On success, `ReceiptLog` is emitted.

`msg.sender` is the paying SCW. It must have approved the contract for `amount` of `token` before the call.

### View functions

```solidity
mapping(bytes32 requestHash => bool settled) public isSettled;
mapping(address token => bool allowed)        public isTokenAllowed;
```

### Owner-only functions

```solidity
function setTokenAllowed(address token, bool allowed) external onlyOwner;
function pause()   external onlyOwner;
function unpause() external onlyOwner;
function _authorizeUpgrade(address newImplementation) internal override onlyOwner;
```

## Events

```solidity
event ReceiptLog(
  address indexed merchant,
  address indexed payer,
  address indexed token,
  uint256 amount,
  bytes32 requestHash
);
```

Emitted on every successful settlement. The three indexed arguments allow efficient `getLogs` filtering by merchant, payer, or token.

## ABI fragments (TypeScript)

```ts
const SETTLEMENT_ABI = [
  "function settle(address merchant, address token, uint256 amount, bytes32 requestHash) external payable",
  "function isSettled(bytes32 requestHash) view returns (bool)",
  "function isTokenAllowed(address token) view returns (bool)",
  "event ReceiptLog(address indexed merchant, address indexed payer, address indexed token, uint256 amount, bytes32 requestHash)",
  "error UnexpectedNativeValue()",
  "error ZeroAddress()",
  "error ZeroAmount()",
  "error ZeroRequestHash()",
  "error TokenNotAllowed(address token)",
  "error AlreadySettled(bytes32 requestHash)",
] as const;
```

## Indexing settlements

A merchant or external indexer can read all settlements without querying the facilitator:

```ts
import { createPublicClient, http, parseAbiItem } from "viem";

const RECEIPT_LOG = parseAbiItem(
  "event ReceiptLog(address indexed merchant, address indexed payer, address indexed token, uint256 amount, bytes32 requestHash)",
);

const logs = await client.getLogs({
  address: SETTLEMENT_CONTRACT,
  event: RECEIPT_LOG,
  fromBlock: BigInt(0),
  toBlock: "latest",
});
```

The reference Playground's live ledger panel uses exactly this pattern.

## Source

The contract source is at [`contracts/src/SettlementContract.sol`](https://github.com/nerochain/nero-x402/blob/main/contracts/src/SettlementContract.sol). The interface is at [`contracts/src/interfaces/ISettlement.sol`](https://github.com/nerochain/nero-x402/blob/main/contracts/src/interfaces/ISettlement.sol). The deployment scripts are in `contracts/script/`.