UK tax overview
UK Income Tax and National Insurance Simplified
This UK income tax and NI simplified guide explains what income tax and National Insurance are at a high level and how they connect to take home pay. You will also see what the calculator includes, what it excludes, and why your payslip can differ.
Published: December 31, 2025 · Updated: December 31, 2025 · By FinToolSuite Editorial
Disclaimer
- Educational purposes only, not financial or tax advice.
- Examples are illustrative and simplified.
- Results depend on your inputs and assumptions and are not guaranteed.
- UK tax and NI depend on allowances, pay type, and personal circumstances.
- See the Privacy Policy for handling details.
Open the salary after tax calculator
Estimate UK take home pay with simplified income tax and NI, then save scenarios.
Quick answers: UK income tax and NI simplified
- UK take home pay is usually reduced by income tax and National Insurance.
- The calculator uses a simplified national model.
- Your payslip can differ because of allowances and employer deductions.
- Use scenarios to test changes like pension percent.
What is UK income tax
Income tax is a tax on earnings. In many systems it is progressive, taxing slices of income at different rates. The calculator uses a simplified national view to estimate this for take home pay.
What is National Insurance
National Insurance is a separate contribution from income tax. It depends on earnings and category in real life. The calculator uses a simplified NI estimate alongside income tax to show take home pay directionally.
What the calculator includes and excludes
Includes
- Simplified income tax estimate.
- Simplified National Insurance estimate.
- Pension percent effect as entered.
Excludes
- Special allowances and reliefs.
- Bonuses and benefits complexity.
- Salary sacrifice detail.
- Other payroll deductions or local taxes.
See calculator limitations and assumptions for more detail.
Illustrative example
| Item | Illustrative amount |
|---|---|
| Gross salary | £50,000 |
| Pension percent | 5% |
| Estimated income tax | £8,000 |
| Estimated NI | £4,000 |
| Estimated net | £38,000 |
Illustrative and simplified; real payslips can differ.
Why your payslip can differ
- Personal allowance changes or thresholds.
- Benefits in kind and salary sacrifice.
- Student loan and other deductions.
- Timing and payroll rounding.
See why payslips differ from estimates for more context.
How to use this in the calculator
- Set origin as UK.
- Enter gross salary and pay frequency.
- Set pension percent if needed.
- Review net, breakdown, and effective tax rate estimates.
Run your own estimate in the salary after tax calculator.
Safe handling and privacy
- Do not upload payslips or personal documents.
- Keep scenario names generic.
- Export files carefully and avoid personal identifiers.
- Review the Privacy Policy before sharing.
FAQs
Does the calculator include National Insurance?
Yes, as a simplified NI estimate alongside income tax.
Why is my NI different on my payslip?
Payslips can reflect categories, thresholds, and timing beyond the simplified model.
Does the calculator include student loan?
No. Student loan deductions are not included.
How does pension percent change tax?
It reduces the taxable base in the model, lowering estimated tax and NI.
Is this an HMRC calculation?
No. It is a simplified national model.
Where can I see the full FAQ?
Visit the salary after tax FAQ.
Why can estimates differ from payslips?
Allowances, salary sacrifice, benefits, and timing make payslips differ.
Is this tax advice?
No. This is educational and simplified.
Try the salary after tax calculator
Estimate UK take home pay, test scenarios, and export a summary.