How a quote picks the tax rate

Tax is resolved from the destination the buyer chose and the product on each line. There is no global fallback: if no jurisdiction is configured for the destination, the quote is refused instead of charging a guessed rate.

Jurisdiction

A state or province row beats the country row for a matching destination. Two rows at the same level are a configuration error.

Product vs category

A product rule beats a category rule, which beats the jurisdiction default. Two rules at the same priority for one target are refused.

Rates

Fractions, not percentages: 0.18 means 18%. A rate that is not between 0 and 1 is refused.

Gross pricing

When prices include tax, the net amount and the tax portion are extracted from the price the buyer sees.

Net pricing

When prices exclude tax, the tax is added on top of the net line amount.

Shipping

Each jurisdiction says whether shipping is taxable. A shipping-option rule can give shipping its own rate.

Exemptions

Only an exemption verified by an operator for the signed-in buyer removes tax. A flag sent by a browser is never trusted.

Rounding

Each line is rounded at the currency’s minor unit, half-up. A jurisdiction with an unsupported rounding policy is refused.

The tax decision is recorded with the accepted order: jurisdiction and rate versions, the rule that selected each rate, the exemption reference, and the tax amount per line. A later settings edit changes future quotes; it does not rewrite an order that was already accepted. Refunds allocate the tax that was originally recorded on the line.