# IERC20PermitAllowed

Interface used by DAI/CHAI for permit

### Functions[​](https://docs.uniswap.org/contracts/v3/reference/periphery/interfaces/external/IERC20PermitAllowed#functions) <a href="#functions" id="functions"></a>

#### permit[​](https://docs.uniswap.org/contracts/v3/reference/periphery/interfaces/external/IERC20PermitAllowed#permit) <a href="#permit" id="permit"></a>

```solidity
  function permit(
    address holder,
    address spender,
    uint256 nonce,
    uint256 expiry,
    bool allowed,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) external
```

Approve the spender to spend some tokens via the holder signature

This is the permit interface used by DAI and CHAI

**Parameters:**[**​**](https://docs.uniswap.org/contracts/v3/reference/periphery/interfaces/external/IERC20PermitAllowed#parameters)

| Name      | Type    | Description                                                                   |
| --------- | ------- | ----------------------------------------------------------------------------- |
| `holder`  | address | The address of the token holder, the token owner                              |
| `spender` | address | The address of the token spender                                              |
| `nonce`   | uint256 | The holder's nonce, increases at each call to permit                          |
| `expiry`  | uint256 | The timestamp at which the permit is no longer valid                          |
| `allowed` | bool    | Boolean that sets approval amount, true for type(uint256).max and false for 0 |
| `v`       | uint8   | Must produce valid secp256k1 signature from the holder along with `r` and `s` |
| `r`       | bytes32 | Must produce valid secp256k1 signature from the holder along with `v` and `s` |
| `s`       | bytes32 | Must produce valid secp256k1 signature from the holder along with `r` and `v` |