Income Tax vs National Insurance Calculator: Complete Tax Breakdown
Understand how income tax and national insurance are calculated separately in your payslip.
CalculatorZone Editorial Team9 min readPublished Updated
Income Tax vs National Insurance: Breaking Down Your Payslip
Your payslip shows various deductions, but two of the biggest are income tax and National Insurance. They're separate calculations, serve different purposes, but both affect your take-home pay. Understanding each helps you plan your finances more accurately.
Income Tax
Income tax funds general government spending: schools, healthcare, infrastructure, defense, and more.
How it works:
- Progressive brackets: 0%, 20%, 40%, 45%
- Most earners pay 20% on income between £12,570 and £50,270
- No tax on personal allowance (first £12,570)
National Insurance
National Insurance funds specific state benefits: pensions, unemployment benefits, sickness benefits, and healthcare.
How it works:
- Different rates for employees (8%) and self-employed Class 4 (6%) in 2026/27
- Lower threshold: starts around £12,570
- Upper rate applies to earnings over £50,270
Key Differences
| Aspect | Income Tax | National Insurance |
|---|---|---|
| Purpose | General government | Specific state benefits |
| Top Rate | 45% | 8% (2% above £50,270) |
Combined Impact on Your Salary
On each extra pound you earn between £12,570 and £50,270 you pay 20% income tax plus 8% National Insurance, 28% in total (2026/27). This is why understanding both is crucial for accurate take-home pay calculations.
Use the correct tax-year inputs
Start by identifying the tax year, where you are tax resident, and which income and deductions are actually included. A calculator can be useful for planning, but payroll timing, tax codes, other income and relief eligibility can make an individual result different from a simplified annual estimate.
- Confirm the relevant tax year and jurisdiction.
- Keep employment, self-employment, savings and dividend income distinct.
- Check the official guidance when a threshold or eligibility rule matters.