> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cloak.ag/llms.txt
> Use this file to discover all available pages before exploring further.

# Fee Model

> How the deployed program computes gross, fee, and net amounts per flow and pool kind

Fees are collected strictly on-chain by the shield-pool program into the mint-scoped treasury
PDA. No other component assesses or deducts fees.

Fees apply **only to flows that move value out of the pool** (`publicAmount < 0`: withdrawals and
swaps). Deposits and shield-to-shield transfers charge no fee.

## Constants

* SOL pool fixed fee: `5_000_000` lamports (`0.005 SOL`)
* Variable fee (all pools): `gross * 3 / 1000` (0.30%)
* SPL pools (USDC/USDT): **variable fee only** — no fixed component, charged in the withdrawn token
* Minimum deposit (SOL pool only): `10_000_000` lamports (`0.01 SOL`); SPL deposits have no
  program-enforced minimum

## Per-flow behavior

* **Deposit (`publicAmount > 0`)**: no fee. The full deposit amount moves into the pool and the
  output commitments encode the full amount.
* **Shield-to-shield transfer (`publicAmount = 0`)**: no fee. No external value moves; the output
  commitments sum to the inputs.
* **Withdrawal (`publicAmount < 0`)**: the destination receives `net = gross - fee`; the treasury
  PDA receives `fee`.
* **Swap (`TransactSwap`, SOL pool only)**: `fee = fixed + variable` is taken from the gross SOL
  at the first transaction; the remainder (`gross - fee`) is what gets swapped.

## Fee math

SOL pool (withdraw/swap):

```
fee = 5_000_000 + gross * 3 / 1000
```

SPL pools (withdraw):

```
fee = gross * 3 / 1000
```

## Worked examples

Withdraw `1 SOL` (`1_000_000_000` lamports) gross:

* Fixed: `5_000_000` lamports
* Variable: `1_000_000_000 * 3 / 1000 = 3_000_000` lamports
* Fee: `8_000_000` lamports — net to recipient: `992_000_000` lamports

Withdraw `100 USDC` (`100_000_000` base units) gross:

* Variable: `100_000_000 * 3 / 1000 = 300_000` base units (`0.30 USDC`)
* Fee: `300_000` base units — net to recipient: `99_700_000` base units

<Tip>
  The Cloak app presents this in reverse: the user enters what the recipient should receive, and
  the app grosses up so `net` equals the entered amount. At the program level the invariant is
  always `net = gross - fee`.
</Tip>

For a user-facing summary with a who-pays table, see [Fees](/guide/fees).