Compute the PAYE on a bonus or 13th cheque. The first USD 700 per year is exempt; only the excess is taxed at your marginal rate.
Enter the bonus amount and your normal monthly taxable income for the month it's paid in.
USD 700 per tax year is exempt under paragraph (o) of the Third Schedule to the Income Tax Act (as substituted by the Finance Act 2024). If part was used earlier (e.g. an interim bonus in June), only the unused balance applies now.
Taxable bonus = Bonus − Available exemption
Apply PAYE bands to your normal taxable income alone.
Add the taxable bonus to that month's income, apply PAYE bands again.
The marginal tax on the bonus is the gap between the two PAYE figures. Add 3% AIDS levy on top.