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

# Validate Coupon

> Public coupon validation for checkout.

```bash theme={null}
POST /api/coupons/validate
```

Public checkout helper. **No seller session.** Rate limited (**20** requests per client window).

Seller CRUD lives at `/api/coupons` and `/api/coupons/{couponId}` with `manageCoupons`.

## Usage

Call from checkout UI before applying a discount. Embed can also pass `couponCode` into create-checkout so Join Markt applies it when opening the invoice.

## Errors

Invalid / expired / ineligible codes return a 4xx JSON `{ error }` (or domain payload). Do not invent client-side discount math that disagrees with the server.