Core API
Look up FIRS reference data used across the other APIs — currencies, tax categories, product/service codes, invoice types, states, countries — plus a few shared "commons" lookups.
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Base path: /v1/core
Most endpoints require an x-api-key header — either a Taxpayer (tpk_) or System
Integrator (sik_) key, see Authentication.
The exception is Invoice Categories,
which is public.
Responses follow the shared envelope described in Errors & Response Format.
