Methodology & Sources

How AfriTaxCalc calculates and verifies its figures

A salary tax calculator is only worth using if its numbers are right. Plenty of online calculators quietly run on outdated tables or copy figures from each other without checking them against the source. We built AfriTaxCalc to do the opposite: every figure in every calculator traces back to an official government publication, is verified by hand, and is locked in place by automated tests before it ever goes live. This page explains exactly how that works, so you can judge our figures for yourself.

Our sources of record

We take tax figures only from primary, official sources — never from other calculators or secondary summaries, which frequently disagree with one another.

South Africa

• Income tax brackets, rebates, medical tax credits, and retirement deduction rules: the South African Revenue Service (SARS), specifically the published tax tables and the Budget 2026 documentation.
• The UIF earnings ceiling: the Department of Employment and Labour, which sets this figure separately from SARS.

Zimbabwe

• PAYE tax tables (USD): the Zimbabwe Revenue Authority (ZIMRA) official tax-table publications, per currency and per period.
• The AIDS levy: ZIMRA's published PAYE guidance.
• NSSA contributions and the insurable-earnings ceiling: the National Social Security Authority (NSSA) directly.

Where different official documents are issued by different bodies — as with South Africa's UIF ceiling, or Zimbabwe's separate ZIMRA and NSSA figures — we go to each responsible authority for its own number rather than relying on any single secondary source.

Our verification process

Every figure goes through the same steps before it appears in a calculator:

1. Sourced from the official document. We record where each figure came from and the date we retrieved it.
2. Hand-computed test cases. Before writing any calculator code, we work out a set of example salaries by hand against the official tables — including the tricky edge cases: income exactly at a tax-free threshold, salaries sitting exactly on a bracket boundary, the contribution-ceiling crossings, and each age or currency variation.
3. Automated tests. Those hand-verified examples are built into the calculator as automated tests. The calculator's answers must match the hand-computed figures before it can be published, and the tests run again every time any figure is updated.
4. Cross-checks. We compare our outputs against established calculators and, where they differ, we investigate to the root cause — and the official source always wins.

This means a change to a tax table is never a quiet edit. It is a deliberate update, re-verified and re-tested, with the change recorded.

"Last verified" dates

Because tax figures change — annually in South Africa's February Budget, and sometimes mid-year in Zimbabwe — every calculator shows the tax year it covers and the date its figures were last verified against the official source. If you ever see a payslip that differs from our calculator, that date is the first thing to check: your employer may not have updated their payroll to the current tables, or a figure may have changed since our last verification. We treat these dates as a promise, not decoration.

What our calculators do and don't include

Our calculators show the statutory deductions that apply to a standard salary: income tax (PAYE), the relevant social contributions (UIF in South Africa, NSSA in Zimbabwe), and applicable levies (SDL for employers in South Africa, the AIDS levy in Zimbabwe). They do not know about deductions specific to your own employment — medical aid scheme contributions beyond the tax credit, pension top-ups, union dues, staff loans, garnishee orders, and so on — because those vary from person to person. That is why a calculator figure and a real payslip can differ without either being wrong.

Not tax advice

AfriTaxCalc provides general information to help you understand how your salary is taxed. It is not tax advice, and it cannot account for every individual circumstance. For decisions that matter, consult a registered tax practitioner or the relevant revenue authority directly.

Questions about our figures or method? Contact us — we take accuracy seriously and welcome corrections.