# Use ERC-20 token permissions

> Learn how to use the ERC-20 token permissions with Advanced Permissions (ERC-7715).

# Use ERC-20 token permissions

[Advanced Permissions (ERC-7715)](../../../concepts/advanced-permissions.md) supports ERC-20 token permission types that allow you to request fine-grained
permissions for ERC-20 token transfers with periodic, fixed allowance, or streaming conditions, depending on your use case.

## Prerequisites

- [Install and set up the Smart Accounts Kit.](../../../get-started/install.md)
- [Configure the Smart Accounts Kit.](../../configure-toolkit.md)
- [Create a session account.](../execute-on-metamask-users-behalf.md#3-set-up-a-session-account)

## ERC-20 allowance permission

This permission type ensures a fixed ERC-20 token allowance.
It allows transfers up to a maximum total amount and doesn't reset by period.

For example, a user signs an ERC-7715 permission that lets your dapp spend up to 50 USDC in total.
After the dapp transfers 50 USDC, no additional transfers are allowed under this permission.

See the [ERC-20 allowance permission API reference](../../../reference/advanced-permissions/permissions.md#erc-20-allowance-permission) for more information.

<Tabs>
<TabItem value="example.ts">

```typescript

// Since current time is in seconds, convert milliseconds to seconds.
const currentTime = Math.floor(Date.now() / 1000)
// 1 week from now.
const expiry = currentTime + 604800

// USDC address on Ethereum Sepolia.
const tokenAddress = '0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238'

const grantedPermissions = await walletClient.requestExecutionPermissions([
  {
    chainId: chain.id,
    expiry,
    // The requested permissions will be granted to the
    // session account.
    to: sessionAccount.address,
    permission: {
      type: 'erc20-token-allowance',
      data: {
        tokenAddress,
        // 50 USDC in WEI format. Since USDC has 6 decimals, 50 * 10^6.
        allowanceAmount: parseUnits('50', 6),
        startTime: currentTime,
        justification: 'Permission to transfer up to 50 USDC in total',
      },
      isAdjustmentAllowed: true,
    },
  },
])
```

</TabItem>
<TabItem value="client.ts">

```typescript

export const walletClient = createWalletClient({
  transport: custom(window.ethereum),
}).extend(erc7715ProviderActions())
```

</TabItem>
</Tabs>

## ERC-20 periodic permission

This permission type ensures a per-period limit for ERC-20 token transfers. At the start of each new period, the allowance resets.

For example, a user signs an ERC-7715 permission that lets a dapp spend up to 10 USDC on their behalf each day. The dapp can transfer a total of
10 USDC per day; the limit resets at the beginning of the next day.

See the [ERC-20 periodic permission API reference](../../../reference/advanced-permissions/permissions.md#erc-20-periodic-permission) for more information.

<Tabs>
<TabItem value="example.ts">

```typescript

// Since current time is in seconds, convert milliseconds to seconds.
const currentTime = Math.floor(Date.now() / 1000)
// 1 week from now.
const expiry = currentTime + 604800

// USDC address on Ethereum Sepolia.
const tokenAddress = '0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238'

const grantedPermissions = await walletClient.requestExecutionPermissions([
  {
    chainId: chain.id,
    expiry,
    // The requested permissions will be granted to the
    // session account.
    to: sessionAccount.address,
    permission: {
      type: 'erc20-token-periodic',
      data: {
        tokenAddress,
        // 10 USDC in WEI format. Since USDC has 6 decimals, 10 * 10^6.
        periodAmount: parseUnits('10', 6),
        // 1 day in seconds.
        periodDuration: 86400,
        justification: 'Permission to transfer 10 USDC every day',
      },
      isAdjustmentAllowed: true,
    },
  },
])
```

</TabItem>
<TabItem value="client.ts">

```typescript

export const walletClient = createWalletClient({
  transport: custom(window.ethereum),
}).extend(erc7715ProviderActions())
```

</TabItem>
</Tabs>

## ERC-20 stream permission

This permission type ensures a linear streaming transfer limit for ERC-20 tokens. Token transfers are blocked until the
defined start timestamp. At the start, a specified initial amount is released, after which tokens accrue linearly at the
configured rate, up to the maximum allowed amount.

For example, a user signs an ERC-7715 permission that allows a dapp to spend 0.1 USDC per second, starting with an initial amount
of 1 USDC, up to a maximum of 2 USDC.

See the [ERC-20 stream permission API reference](../../../reference/advanced-permissions/permissions.md#erc-20-stream-permission) for more information.

<Tabs>
<TabItem value="example.ts">

```typescript

// Since current time is in seconds, convert milliseconds to seconds.
const currentTime = Math.floor(Date.now() / 1000)
// 1 week from now.
const expiry = currentTime + 604800

// USDC address on Ethereum Sepolia.
const tokenAddress = '0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238'

const grantedPermissions = await walletClient.requestExecutionPermissions([
  {
    chainId: chain.id,
    expiry,
    // The requested permissions will be granted to the
    // session account.
    to: sessionAccount.address,
    permission: {
      type: 'erc20-token-stream',
      data: {
        tokenAddress,
        // 0.1 USDC in WEI format. Since USDC has 6 decimals, 0.1 * 10^6.
        amountPerSecond: parseUnits('0.1', 6),
        // 1 USDC in WEI format. Since USDC has 6 decimals, 1 * 10^6.
        initialAmount: parseUnits('1', 6),
        // 2 USDC in WEI format. Since USDC has 6 decimals, 2 * 10^6.
        maxAmount: parseUnits('2', 6),
        startTime: currentTime,
        justification: 'Permission to use 0.1 USDC per second',
      },
      isAdjustmentAllowed: true,
    },
  },
])
```

</TabItem>
<TabItem value="client.ts">

```typescript

export const walletClient = createWalletClient({
  transport: custom(window.ethereum),
}).extend(erc7715ProviderActions())
```

</TabItem>
</Tabs>