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

# Rules & rates

> The commission rate, its fixed and percentage forms, and per-currency amounts.

This page covers how a commission rate is modeled and the two ways it can
express the marketplace's cut.

## Commission rate

A commission rate is the number the marketplace takes from a sale. It's
represented by the `CommissionRate` data model (table `commission_rate`, id
prefix `comrate`). A rate has a `name`, a unique `code`, a `type`, and a
`value`, plus the `include_tax` and `include_shipping` toggles.

```ts theme={null}
const { result } = await createCommissionRatesWorkflow(container).run({
  input: [
    {
      name: "Standard",
      type: CommissionRateType.PERCENTAGE,
      value: 10,
    },
  ],
})
```

A rate is either **percentage** or **fixed**, set by `type`
(`CommissionRateType`):

| Type         | How `value` is read                                   |
| ------------ | ----------------------------------------------------- |
| `percentage` | A percent of the line's base amount (e.g. `10` → 10%) |
| `fixed`      | A flat amount deducted per line                       |

<Note>
  A rate's `code` is unique. When you create a rate without one, the module
  auto-generates a URL-safe code from the `name` (e.g. `"Standard"` →
  `standard-a1b2c3`).
</Note>

## Per-currency amounts

A fixed rate can carry a different amount for each currency. This is
represented by the `CommissionRateValue` data model (table
`commission_rate_value`, id prefix `comval`). Each value pairs a `currency_code`
with an `amount`, and the calculation picks the value matching the order's
currency.

```ts theme={null}
await createCommissionRatesWorkflow(container).run({
  input: [
    {
      name: "Flat fee",
      type: CommissionRateType.FIXED,
      value: 5, // fallback when no per-currency value matches
      values: [
        { currency_code: "usd", amount: 5 },
        { currency_code: "eur", amount: 4 },
      ],
    },
  ],
})
```

<Tip>
  When no `values` entry matches the order's currency, a fixed rate falls back
  to its scalar `value`. Percentage rates ignore `values` entirely. A percent
  is currency-independent.
</Tip>

## The global commission

Every marketplace has exactly one **Global Commission**. This is the rate with
`is_default` set to `true`. Mercur seeds it at boot (a `0%` percentage rate
named `Default`) so a rate always exists, and it applies whenever no
more-specific rate matches a line.

<Note>
  The global rate is also the **only** rate that can commission shipping. See
  [Rule matching](/platform/commission/concepts/rule-matching) for how
  specificity and shipping are resolved.
</Note>