Choose one calculation model
Progressive slices tax each portion of income at its own rate. Base-plus-marginal bands choose the matching band, then add a fixed base to the marginal tax above that band’s lower boundary. Do not add both methods together.
A fictional example
For demonstration only: the first 1,000 at 0%, the next 1,000 at 10%, and the remaining amount at 20% give tax of 200 on income of 2,500. These invented brackets are not a country’s tax rules.
Test the boundaries
Simulate incomes immediately below, at, and above each threshold. Check effective dates, contribution caps, allowances, and rounding. Monthly and annual inputs must match the profile frequency; there is no automatic annualization.
Keep the source and version
Record source links and give each revision a new version. Imported JSON remains user-configured. Employer responsibility and any required qualified review remain separate from the software’s arithmetic.
Put it into practice.
Start with a blank document or a fictional sample. Your details stay in your browser.
Create a salary slip →