> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/Privacy-Cash/privacy-cash/llms.txt
> Use this file to discover all available pages before exploring further.

# update_global_config

> Update global fee configuration for SOL and SPL token transactions

## Overview

The `update_global_config` instruction allows the program authority to modify the global fee settings that apply to all SOL and SPL token transactions.

Fees are specified in basis points (1 basis point = 0.01%).

<Note>
  Only the program authority can call this instruction. At least one parameter must be provided.
</Note>

## Function Signature

```rust theme={null}
pub fn update_global_config(
    ctx: Context<UpdateGlobalConfig>,
    deposit_fee_rate: Option<u16>,
    withdrawal_fee_rate: Option<u16>,
    fee_error_margin: Option<u16>
) -> Result<()>
```

## Parameters

<ParamField path="deposit_fee_rate" type="Option<u16>">
  Deposit fee rate in basis points (0-10000).

  * `0` = 0% (free deposits)
  * `25` = 0.25%
  * `100` = 1%
  * `1000` = 10%
  * `10000` = 100% (maximum)

  Pass `None` to leave unchanged.
</ParamField>

<ParamField path="withdrawal_fee_rate" type="Option<u16>">
  Withdrawal fee rate in basis points (0-10000).

  * `0` = 0% (free withdrawals)
  * `25` = 0.25% (default)
  * `50` = 0.5%
  * `100` = 1%
  * `10000` = 100% (maximum)

  Pass `None` to leave unchanged.
</ParamField>

<ParamField path="fee_error_margin" type="Option<u16>">
  Acceptable fee margin in basis points (0-10000). Allows fees to be within a range:

  * `0` = Exact fee required
  * `500` = ±5% (default)
  * `1000` = ±10%

  Formula: `expected_fee * (1 - margin/10000) <= actual_fee <= expected_fee`

  Pass `None` to leave unchanged.
</ParamField>

## Accounts

<ParamField path="global_config" type="Account<GlobalConfig>" required>
  Global configuration account. PDA: `["global_config"]`.

  * **Mutable**: Yes
  * **Authority check**: Must be owned by the signer
</ParamField>

<ParamField path="authority" type="Signer" required>
  The program authority. Must match the global\_config's authority field.

  * **Signer**: Yes
</ParamField>

## Code Examples

### Update Withdrawal Fee

```typescript theme={null}
import * as anchor from "@coral-xyz/anchor";
import { Program } from "@coral-xyz/anchor";
import { PublicKey } from "@solana/web3.js";

const program = anchor.workspace.Zkcash as Program<Zkcash>;
const authority = anchor.web3.Keypair.generate();

const [globalConfigPDA] = PublicKey.findProgramAddressSync(
  [Buffer.from("global_config")],
  program.programId
);

// Update withdrawal fee to 0.5% (50 basis points)
await program.methods
  .updateGlobalConfig(
    null, // Don't change deposit fee
    50,   // 0.5% withdrawal fee
    null  // Don't change error margin
  )
  .accounts({
    globalConfig: globalConfigPDA,
    authority: authority.publicKey
  })
  .signers([authority])
  .rpc();
```

### Update All Fee Settings

```typescript theme={null}
// Update all fee parameters at once
await program.methods
  .updateGlobalConfig(
    10,   // 0.1% deposit fee
    30,   // 0.3% withdrawal fee
    1000  // 10% error margin
  )
  .accounts({
    globalConfig: globalConfigPDA,
    authority: authority.publicKey
  })
  .signers([authority])
  .rpc();

console.log("All fee settings updated");
```

### Make Deposits Free

```typescript theme={null}
// Set deposit fee to 0%
await program.methods
  .updateGlobalConfig(
    0,    // Free deposits
    null, // Keep withdrawal fee unchanged
    null  // Keep error margin unchanged
  )
  .accounts({
    globalConfig: globalConfigPDA,
    authority: authority.publicKey
  })
  .signers([authority])
  .rpc();
```

## Fee Calculation Examples

<AccordionGroup>
  <Accordion title="Deposit Fee Calculation">
    With deposit fee rate of 25 basis points (0.25%):

    ```
    Deposit: 10 SOL
    Fee: 10 * 0.0025 = 0.025 SOL
    User receives: 9.975 SOL in private balance
    ```
  </Accordion>

  <Accordion title="Withdrawal Fee Calculation">
    With withdrawal fee rate of 50 basis points (0.5%):

    ```
    Withdrawal: 5 SOL
    Fee: 5 * 0.005 = 0.025 SOL
    User receives: 4.975 SOL
    Fee recipient receives: 0.025 SOL
    ```
  </Accordion>

  <Accordion title="Fee Error Margin">
    With error margin of 500 basis points (5%):

    ```
    Expected fee: 0.025 SOL
    Minimum acceptable: 0.025 * 0.95 = 0.02375 SOL
    Maximum acceptable: 0.025 SOL (no upper bound)

    This allows slightly lower fees to account for rounding errors.
    ```
  </Accordion>
</AccordionGroup>

## Basis Points Reference

<CardGroup cols={2}>
  <Card title="Common Fee Rates">
    * 0 = 0% (free)
    * 1 = 0.01%
    * 10 = 0.1%
    * 25 = 0.25%
    * 50 = 0.5%
    * 100 = 1%
    * 250 = 2.5%
    * 500 = 5%
    * 1000 = 10%
  </Card>

  <Card title="Fee Error Margins">
    * 0 = No margin (exact)
    * 100 = ±1%
    * 500 = ±5%
    * 1000 = ±10%
    * 2000 = ±20%
  </Card>
</CardGroup>

## State Changes

### GlobalConfig

* `deposit_fee_rate`: Updated if provided (otherwise unchanged)
* `withdrawal_fee_rate`: Updated if provided (otherwise unchanged)
* `fee_error_margin`: Updated if provided (otherwise unchanged)

All other fields remain unchanged.

## Behavior

1. Validates each provided fee rate is ≤ 10000 (100%)
2. Updates only the provided parameters
3. Emits program log messages for each updated field
4. Changes apply immediately to all subsequent transactions

<Warning>
  Fee changes apply immediately. Ongoing transactions use the fee rates at the time of execution.
</Warning>

## Authorization

The signer must be the global config's authority:

```rust theme={null}
#[account(
    mut,
    seeds = [b"global_config"],
    bump = global_config.bump,
    has_one = authority @ ErrorCode::Unauthorized
)]
pub global_config: Account<'info, GlobalConfig>,
```

## Errors

<ResponseField name="Unauthorized" type="Error">
  Thrown when the signer is not the global config's authority.
</ResponseField>

<ResponseField name="InvalidFeeRate" type="Error">
  Thrown when any fee rate parameter exceeds 10000 (100%).
</ResponseField>

## Program Log Output

When successful, the instruction logs each updated field:

```
Deposit fee rate updated to: {rate} basis points
Withdrawal fee rate updated to: {rate} basis points
Fee error margin updated to: {margin} basis points
```

## Reading Current Configuration

```typescript theme={null}
// Fetch current global config
const config = await program.account.globalConfig.fetch(globalConfigPDA);

console.log(`Deposit fee: ${config.depositFeeRate} basis points`);
console.log(`Withdrawal fee: ${config.withdrawalFeeRate} basis points`);
console.log(`Fee error margin: ${config.feeErrorMargin} basis points`);
console.log(`Authority: ${config.authority.toString()}`);
```

## Default Configuration

Initialized by the `initialize` instruction:

```rust theme={null}
deposit_fee_rate: 0,      // 0% - Free deposits
withdrawal_fee_rate: 25,  // 0.25%
fee_error_margin: 500,    // 5%
```

## Best Practices

<Steps>
  <Step title="Test fee changes">
    Test on devnet before updating mainnet configuration.
  </Step>

  <Step title="Announce changes">
    Notify users before making fee changes, especially increases.
  </Step>

  <Step title="Set reasonable margins">
    Use 5-10% error margins to account for precision and rounding.
  </Step>

  <Step title="Monitor impact">
    Track fee collection and transaction volume after changes.
  </Step>
</Steps>

## See Also

* [initialize](/reference/instructions/initialize) - Set initial fee configuration
* [transact](/reference/instructions/transact) - How fees apply to SOL transactions
* [transact\_spl](/reference/instructions/transact-spl) - How fees apply to SPL transactions