Architecture

A TaxQuery carries the amount, whether it is net or gross, the buyer jurisdiction (place of supply, resolved from laravel-geo), the customer type, the product category, the selling entity's registrations, and an optional buyer exemption.

DefaultTaxCalculator reads the place of supply's tax profile, selects the TaxRegime keyed by its regimeModule, and delegates. The regime returns a TaxAssessment: treatment, the net/tax/gross split, the place of supply, the rate applied, a human-readable reason, and (only when a buyer certificate drove the outcome) the applied exemption.

Exemption override

After the regime returns its verdict, the calculator applies any TaxQuery::$exemption deny-by-default: a valid exemption that covers the taxed jurisdiction rewrites a would-be Standard line to Exempt (net kept, tax 0), and leaves every other treatment — reverse-charge, not-registered, zero-rated, already-exempt — untouched. See exemptions.

Own the logic, source the data

• Logic (owned): place-of-supply, B2B/B2C reverse-charge determination, inclusive/exclusive handling, rate application and rounding, and the assessment itself all live in the engine.
• Data (sourced): the rate number comes from a TaxRateSource — an EU TEDB feed, the SST files, or a commercial adapter. The engine decides whether and how to apply it.

Deny-by-default

• No regime modelled for a jurisdiction → UnsupportedJurisdiction.
• No rate available from the source → UnresolvedTaxRate.

Neither ever degrades to a silent 0% — a wrong tax outcome is a real liability.