Line Items, Tax & Order Details

When you create a checkout session, you can pass full itemized details. Genius Checkout uses them in four places:

1. The checkout page (so the customer sees what they're paying for)
2. The success page and downloadable receipt
3. The payment gateway (PowerTranz TaxAmount field, etc.)
4. Webhook payloads (so your backend can match on metadata.order_id, etc.)

Example

{
  "line_items": [
    { "name": "Island Rum Cake", "quantity": 2, "unit_amount": 2500, "description": "750g" },
    { "name": "Shipping", "quantity": 1, "unit_amount": 1500 }
  ],
  "subtotal": 6500,
  "tax_name": "GCT",
  "tax_rate": 0.15,
  "tax_amount": 975,
  "amount": 7475
}

Field reference

Field	Type	Description
line_items[].name	string	Item name shown on checkout and receipt
line_items[].quantity	integer	How many
line_items[].unit_amount	integer	Per-unit price in the smallest currency unit (cents)
line_items[].description	string	Optional detail line under the item name
subtotal	integer	Sum of line items before tax (cents)
tax_name	string	Label like GCT, VAT, Sales Tax
tax_rate	number	Decimal (0.15 = 15%) — used for display
tax_amount	integer	Pre-computed tax in cents — what's actually charged
amount	integer	Total charged (cents). Should equal subtotal + tax_amount.

Validation

amount is the source of truth for the charge. subtotal + tax_amount is shown to the customer. If they don't match exactly, the customer sees the breakdown but is charged amount — keep them consistent unless you have a reason not to.

Common patterns

No tax

Omit tax_name, tax_rate, tax_amount. amount should equal subtotal.

Tax included in price

Some Caribbean jurisdictions include VAT in the displayed price. Set tax_name and tax_amount to communicate the embedded tax to the gateway, but compute amount to match the price the customer expects.

Subscription with one-off setup fee

Pass two line items — Setup fee and First month subscription. The token created from the charge can be used for renewals at just the recurring amount. See Tokenization.