What does that bonus or share sale actually cost you?
The marginal rate on your next rand, and what you keep after tax, on a bonus, extra income, or a capital gain.
South Africa taxes income on a sliding scale. Your next rand is taxed at your marginal rate, not your average one. A bonus is never all taxed at your top rate, and a capital gain is not a flat separate tax. Enter your numbers below to see the real figure, and the split between what you keep and what SARS takes.
Everything is computed in your browser; your numbers never leave this page.
How this is computed
Brackets, not a single rate
South Africa taxes individuals on a sliding scale of brackets. Each slice of your income is taxed at that bracket's rate, and a rebate is subtracted at the end. Two numbers come out of this that people routinely confuse. Your marginal rate is the rate on your next rand, the bracket you are in. Your effective rate is total tax divided by total income, and it is always lower.
Tax on a bonus: the aggregation method
The tax on a bonus is not the bonus times your top rate. It is the tax on your income with the bonus minus the tax on your income without it. Only the part of the bonus that crosses into a higher bracket is taxed at that higher rate.
tax on bonus = tax(income + bonus) − tax(income)
Worked example: a R38 000 bonus on R520 000 (2027 tax year)
Tax without the bonus: R104 617. Tax with the bonus (on R558 000): R117 787.
Tax on the bonus: R13 170. That is an average of 34.7% on the bonus, because R10 200 of it fills the rest of the 31% band and R27 800 falls into the 36% band. None of it is taxed at 45%, and it does not change the tax on the first R520 000.
Capital gains tax for individuals
CGT is part of income tax, not a separate flat tax. Proceeds minus base cost gives your capital gain. You deduct the annual exclusion, then 40% of the remaining gain (the inclusion rate for individuals) is added to your taxable income and taxed at your marginal rate.
taxable gain = (proceeds − base cost − exclusions) × 40% CGT = tax(income + taxable gain) − tax(income)
Worked example: a R300 000 share gain on R1 100 000 income (2027 tax year)
Gain R300 000, less the annual exclusion R50 000 → R250 000, times 40% → R100 000 added to income. Taxed at the 41% marginal rate → CGT R41 000.
The effective rate on the whole gain is 13.7%, well below the 18% ceiling. That is because of the exclusion, and because the marginal rate here is 41%, not 45%. Sold as a primary residence instead, the first R3 000 000 of gain would be excluded entirely.
Common questions
After reading this section, if you still have questions, feel free to contact us however you want.
Is the whole bonus taxed at my highest rate?
No. Only the slice of the bonus that pushes into a higher bracket is taxed at that higher rate. The rest is taxed at your existing rate. That is why the average rate on a bonus sits between two bracket rates.
Why is my marginal rate higher than my effective rate?
Your marginal rate is the rate on your next rand. Your effective rate is total tax over total income. It is lower, because your earlier rands were taxed in lower brackets and the rebate reduces the start.
Is capital gains tax a separate 18% tax?
No. 18% is the maximum effective rate for an individual (40% of the gain taxed at the 45% top marginal rate). Most people pay less, because only 40% of the net gain is taxed at all, and at their own marginal rate.
Does this compute my PAYE for the month?
No. This shows your final tax on the amount you enter, not the PAYE your employer withholds in the bonus month (which annualises differently and often over-withholds, then settles at assessment).
Do my numbers leave my computer?
No. Every calculation runs in your browser. Nothing is uploaded, stored, or sent to a server — which also keeps it clean under POPIA.
Who built this
Rian Cronje comes to personal finance from the outside. After 25 years in corporate finance: Group Financial Controller roles, multi-currency consolidations and digital transformation, the unglamorous rigour of making a business’s accounts actually reconcile - he found almost none of that discipline had reached the way individuals track their own wealth. He is not an advisor; he has nothing to sell you about where to put your money. He built Monverdo to close that gap: to hold a person’s wealth to the standard a company holds its own books, and to break down the jargon that keeps capable people. him once included, locked out of their own numbers.
This calculator publishes the standard SARS textbook method for marginal tax and capital gains tax for individuals, for the selected year of assessment. It is an educational tool, not tax or financial advice, and does not cover every situation (for example provisional tax, foreign assets, or PAYE withholding). Methodology by Rian Cronje, 25 years senior international finance and Group Financial Controller experience. Monverdo is a wealth-tracking product in development. Join the waitlist to track your accruing tax position automatically.
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