How ZARWise works out its figures
By AfroTech.
ZARWise is only useful if its numbers are right and current. This page explains where they come from, how the calculations work, how they're kept up to date and how they're checked.
Where the figures come from
Every rate, table and fee comes from an official or primary source, never from another calculator site:
- SARS: Rates of tax for individuals, 2027 tax year
- SARS: Medical tax credit rates
- SARS: Budget 2026 FAQ (retirement deduction cap, lump sum tables, interest exemption, CGT exclusions)
- SARS: Tax-free investments (annual and lifetime limits)
- SARS: Capital gains tax inclusion rate
- SARS: Transfer duty
- Deeds Registries fee schedule, Government Gazette 54225, Notice 7180, effective 1 April 2026
- Law Society of South Africa, Conveyancing Guideline of Fees, effective 1 July 2026
- South African Reserve Bank: repo rate 7,25% from 25 September 2026
- National Credit Regulations, regulation 42: maximum interest rates (GN 1080, Government Gazette 39379)
- Unemployment Insurance Contributions Act: 1% employee contribution, R17 712 monthly ceiling
- National Credit Regulator: initiation fee and monthly service fee caps
- SARS: Tax implications of withdrawing from the two-pot retirement system
A few items vary from firm to firm, such as attorneys' disbursements and a bank's bond initiation fee. Those are typical market figures, and the calculators label them as estimates.
How the calculators work
- Take-home pay and income tax: PAYE uses SARS's annualised method: monthly pay × 12, the 2026/27 tax table, minus the rebate for your age and medical tax credits, divided by 12. Income tax for the year adds other income and interest above the R 23 800 exemption. Retirement contributions are deducted up to 27,5% of income and R 430 000 a year. UIF is 1% up to the R 17 712 monthly ceiling.
- Bonds and loans: the standard amortising formula banks use, with interest charged monthly on the balance. Car finance supports a balloon payment, and car and personal loans include the initiation and service fees the National Credit Act allows.
- Affordability: the common bank guideline that the repayment stays below 30% of gross income, after other debt.
- Transfer costs: transfer duty from the SARS table, attorneys' fees from the Law Society guideline (effective 1 July 2026), and Deeds Office fees from the tariff in Government Gazette 54225, Notice 7180.
- Retirement: RA tax savings compare your tax with and without the contribution. Two-pot withdrawals are added to your income and taxed at your marginal rate. Lump sums use SARS's withdrawal and retirement tables, cumulatively with earlier lump sums.
- Savings and property: Tax-free savings projects monthly contributions at a growth rate you choose, within the R 46 000 annual and R 500 000 lifetime limits. Capital gains tax applies the exclusions and adds 40% of the gain to your income.
Every calculator runs in your browser. Nothing you type is sent anywhere or stored.
How the figures are kept current
- Prime rate: checked every week, and updated within days of each Reserve Bank decision. Last checked 9 October 2026.
- Tax tables: updated after each February Budget, once SARS publishes the new tables, for the tax year starting 1 March.
- Property fees: the Deeds Office tariff (usually 1 April) and the Law Society guideline (mid-year).
- Everything else (National Credit Act caps, two-pot rules, VAT): checked at least once a year and whenever the law changes.
Every page shows when its figures were last checked: all tables and fees on 30 September 2026. A built-in check flags any figure that's overdue. Changes are listed in the changelog.
How the figures are tested
100 automated checks run before any update can go live. They compare the calculators against figures worked out by hand from the official tables. For example, the tax on R360 000 a year, the transfer duty on a R2 million home, and the tax on a R1 million retirement lump sum. Other checks confirm that each tax table is internally consistent, and that income exactly at a tax threshold pays no tax.
The guides, salary pages and reference pages are calculated from the same data as the calculators, so they can't fall out of step. If any page contains a broken value, the update is blocked and the previous version stays online.
What the calculators don't cover
The results are estimates for planning, for common situations. They don't cover every case: foreign income, the additional medical expenses tax credit, provisional tax, trusts and companies are outside their scope. They aren't tax, legal or financial advice. Your payslip, your bank's quote, your attorney's pro forma account or your SARS assessment is the final word.
Found something that looks wrong? Please tell us. See the editorial policy for how corrections are handled.