# Tax calculation regression: pre-release checklist

Source: https://releasefailures.com/incidents/tax-calculation-regression/
Content version: 1.0.0
Verified on: 2026-10-21
Licence: CC BY 4.0

Definition: Tax or VAT is computed with the wrong rate or jurisdiction after a rules or data update.
- [ ] PR-01 Add a unit test that computes the tax amount on each tax report line from the current rate table entry, not from a literal multiplier such as 0.2. (test class: Unit tests)
- [ ] PR-02 Search tax report formulas for literal rate values and confirm each one matches the current rate table entry for that jurisdiction. (test class: Unit tests)
- [ ] PR-03 Add a unit test that fails when a tax report line's taxable amount and tax amount use different rates. (test class: Unit tests)
- [ ] PR-04 Add an integration test that saves a reservation item with a price override and the tax dropdown disabled, then reads the stored tax code back from the database. (test class: Integration tests)
- [ ] PR-05 Confirm the endpoint that stores tax codes rejects an empty array instead of saving it. (test class: Integration tests)
- [ ] PR-06 Add an integration test that generates an invoice from a booking with a price override and compares the invoice VAT rate with the rate table entry for that item. (test class: Integration tests)