# Discounts, gift cards & store credit

Kustom has no discount UI — every reduction is an order line. The shapes a discount, a multi-buy offer, a gift card and store credit each take, and how VAT is calculated on them.

Kustom has no discount UI. Every reduction is expressed in the order lines, which means a
promotion is something your own system prices and Kustom renders — not a feature you
switch on.

**Coming soon: better support inside Kustom Checkout.** Handling discounts, gift cards and store
credit in the checkout itself is on the way. Until then, express every reduction as an order
line, as shown below.

## A discount on one line

A 20% reduction on a shirt at 25% VAT uses `total_discount_amount` on that line, with
`total_amount` already reduced:

```json
{
  "type": "physical",
  "name": "White t-shirt",
  "reference": "12-345-ABC",
  "quantity": 1,
  "unit_price": 30000,
  "tax_rate": 2500,
  "total_amount": 25000,
  "total_discount_amount": 5000,
  "total_tax_amount": 5000
}
```

## An order-level discount

Its own line, with negative amounts and `type: "discount"`. A fixed 10.00 off at 25% VAT:

```json
{
  "type": "discount",
  "name": "10.00 discount",
  "reference": "12-345-ABC-discount",
  "quantity": 1,
  "unit_price": -1000,
  "tax_rate": 2500,
  "total_amount": -1000,
  "total_tax_amount": -200
}
```

## Multi-buy offers

Three for the price of two, and so on, are the same shape as an order-level discount: work
out the cash value of the offer, put it on a `discount` line as a negative `total_amount`
and derive `total_tax_amount` from it with the formula in [How VAT lands on a
reduction](#how-vat-lands-on-a-reduction).

## Gift cards and store credit

These are **not** discounts, because no VAT is due when they are sold — only when they are
spent. Redeem them as a negative line at 0% tax, typed `gift_card`:

```json
{
  "type": "gift_card",
  "name": "Gift card",
  "reference": "voucher",
  "quantity": 1,
  "unit_price": -10000,
  "tax_rate": 0,
  "total_amount": -10000,
  "total_tax_amount": 0
}
```

Store credit issued for a return is handled the same way, typed `store_credit`. Loyalty points and bonus cheques
are agreed case by case with Kustom, but a bonus cheque generally behaves as a voucher.

A voucher that covers the whole cart leaves a zero-amount order, which needs no
configuration: Kustom shows no payment methods, leaves the purchase button active and the
confirmation page reports a completed zero-amount order.

## How VAT lands on a reduction

VAT is calculated on the **discounted** price. The tax on any line is:

```
total_amount - total_amount * 10000 / (10000 + tax_rate)
```

Whatever shape a reduction takes below, `order_amount` must still equal the sum of the
line totals. That's the invariant the whole order is checked against.

## Related

- [Order lines and tax](/checkout/tax-and-order-lines/) — the order line in full
- [Checkout options](/checkout/checkout-options/) — the rest of the order's configuration
- [Checkout API reference](/api/checkout/) — the authoritative schema for every field here