How we make SA tax law deterministic.
Every number our free tax tools produce comes from a pure calculation engine that is regression-tested against deterministic goldens anchored to figures SARS itself publishes. A wrong number can't ship — but deterministic is not the same as infallible. Here is exactly what that means.
A wrong calculation can't merge
The tax logic lives in a single pure module with no UI, no network, and no hidden state — the same inputs always produce the same output. That module is covered by a regression test suite of golden cases: fixed inputs paired with the exact expected result.
- ✓Goldens are anchored to SARS published rate tables, rebates and thresholds for the year of assessment.
- ✓Worked examples from the Fourth Schedule and SARS guidance are encoded as test cases.
- ✓Continuous integration runs the suite on every change — if any golden drifts, the build fails and the change cannot be merged.
- ✓The same verified engine powers both this public tool and the Practacular product.
Deterministic ≠ infallible
Determinism guarantees consistency, not correctness for every situation in the world. Our goldens cover the cases that are published and well-understood. They do not cover every edge of South African tax law.
- !Goldens cover published cases — unusual structures, niche elections, and disputed interpretations may differ.
- !Tax legislation changes; rate tables and thresholds are updated per year of assessment, and a tool may lag a recent amendment.
- !These tools do not know your full circumstances — they compute from the inputs you provide.
- !Nothing here is a binding tax opinion. Professional judgment by a registered tax practitioner is still required.
Use these tools to get an accurate, reproducible first number — then let a professional confirm it against your full position. That is exactly how the Practacular product works: AI drafts and computes, every output cites its source, and a human approves.
Practacular is a practice management tool and does not constitute formal tax advice. Always consult a registered tax practitioner for binding opinions.