0006. Country rules are data

• Status: Accepted
• Date: 2026-10-27

Context

Tax rates, rounding rules and receipt requirements differ by country and change over time. Hard-coding Malaysian rules would make every other country a fork.

Decision

Country-specific rules (tax codes and rates, cash rounding, required receipt fields) live as data in a country pack, validated by a JSON schema. Malaysia (packages/country-my) is the first pack. packages/core implements the generic calculations and reads rates and codes from the pack.

Consequences

• No Malaysian rate or code is hard-coded outside packages/country-my.
• Each pack ships test vectors (fixtures/vectors.json) that any implementation can check itself against.
• Supporting another country is a contribution of a new pack, not a fork.