Line Items & Pricing

Each invoice contains one or more line items. Every line item has:

Field	Required	Description
Description	Yes	What you’re billing for (max 500 characters)
Quantity	Yes	Supports decimal quantities (e.g., 2.5 hours)
Unit price	Yes	Per-unit amount in USD
Discount	No	Percentage (0-100%) or fixed dollar amount
Product link	No	Tie to a catalog product for inventory tracking
Tax rate	No	Only shown with itemized tax: a per-line override of the default rate

Discounts

Discounts operate at two levels:

1. Line-level — a percentage or fixed amount applied to a single line item
2. Order-level — a coupon or promotion code applied to the entire invoice

Line-level discounts are calculated first, then order-level coupons apply to the discounted subtotal.

Tax calculation

Tax is computed on the pre-discount subtotal using your merchant-level tax rate (set in Settings > Basic Info). You can override the rate or set an explicit tax amount per invoice.

The tax is labelled the way your business country names it: “GST” in Australia, “MwSt.” in Germany, “Sales tax” in the United States. Only the wording changes; the calculation is the same everywhere.

Itemized tax (per-line rates)

Merchants who have set a tax ID and at least one active rate use itemized tax (formerly “VAT mode”), available where the country’s tax works that way (VAT and GST countries). See Tax Configuration. With itemized tax, the flat rate above is replaced by per-line rates:

• Each line picks a tax rate (defaulting to the merchant’s default rate, or the linked product’s price’s own default rate if one is set)
• A single invoice can mix rates — e.g. standard-rated goods and reduced-rated food on one invoice
• The rate is snapshotted onto the line at creation time, so later edits to a rate preset don’t change already-created invoices
• The resulting invoice shows a breakdown grouped by rate instead of a single tax line, in your tax’s name (“GST @ 10%”, “MwSt. @ 19%”). See PDF & Email

Tipping

Invoices support a per-order tip amount, primarily used in the Immediate (POS) flow. The tip is separate from the subtotal and tax, and it is added to the charge exactly once.

The amount a customer is charged on-chain is:

grand total = subtotal − discount + tax + tip

Tax is never charged on the tip, and the tip is not eligible for coupon discounts. The amount field on a payment (the transaction and payment link) is the tip-excluded charge (subtotal − discount + tax); the tip is carried separately as tip_amount and combined into the grand total at the point of payment. This keeps the tip counted a single time across the pay page, receipts, refunds, and analytics.