The UK Tax System: A Beginner's Guide for 2025/26
By calculatemysalary.co.uk Editorial Team
How the UK tax system actually works — income tax bands, National Insurance, tax codes, and what they all mean for your take-home pay.
The UK tax system can feel bewildering when you're starting out — or even when you've been working for years and never really looked into it. This guide covers the fundamentals: income tax bands, National Insurance, your personal allowance, and the jargon that appears on your payslip.
How Income Tax Works
UK income tax is progressive. You pay higher rates only on the portion of income that falls into each band — not on the whole lot. For 2025/26:
| Band | Income range | Rate |
|---|---|---|
| Personal Allowance | £0 – £12,570 | 0% |
| Basic Rate | £12,571 – £50,270 | 20% |
| Higher Rate | £50,271 – £125,140 | 40% |
| Additional Rate | Over £125,140 | 45% |
So if you earn £30,000, you pay nothing on the first £12,570 and 20% on the remaining £17,430. That's £3,486 in income tax — an effective rate of about 11.6%.
If you earn over £100,000, your Personal Allowance shrinks by £1 for every £2 above the threshold, disappearing entirely at £125,140. See GOV.UK for the full details.
National Insurance Contributions (NIC)
National Insurance gets deducted alongside income tax. It funds the State Pension, NHS, and other state benefits.
For employees in 2025/26:
- 8% on earnings between £12,570 and £50,270
- 2% on earnings above £50,270
Your employer also pays NI — 15% on your earnings above £5,000/year from April 2025. That doesn't come out of your pay, but it's part of your total employment cost.
If you're self-employed, you pay Class 2 and Class 4 NI through Self Assessment.
Tax Codes
Your tax code tells your employer how much income tax to deduct. The most common code is 1257L, which means you get the standard Personal Allowance of £12,570.
Other codes you might see:
- BR — all income taxed at basic rate (common for second jobs)
- D0 — all income taxed at higher rate
- K codes — you owe extra tax from previous years or have taxable benefits
- 0T — no Personal Allowance applied (often means HMRC needs more information from you)
If your code looks wrong, don't ignore it. Check your personal tax account on GOV.UK or call HMRC on 0300 200 3300.
Other Tax-Free Allowances
Beyond the Personal Allowance, you may benefit from:
- Personal Savings Allowance: Up to £1,000 of savings interest tax-free (basic rate taxpayers), £500 for higher rate
- Dividend Allowance: £500 of dividend income tax-free
- Marriage Allowance: Transfer up to £1,260 of unused Personal Allowance to a spouse or civil partner — worth up to £252/year
How to Read Your Payslip
Your payslip breaks down what you earned and what was deducted. The key lines:
- Gross Pay — total earnings before deductions
- Income Tax — tax calculated from your earnings and tax code
- National Insurance — your employee NI contributions
- Pension — your workplace pension deduction
- Net Pay — what actually arrives in your bank account
If the numbers don't look right, run your salary through our salary calculator to double-check.
What to Do Next
Once you understand tax bands, NI rates, and your tax code, you can sanity-check your payslip and compare job offers properly. If something seems off, check your tax code first — it's the most common source of payroll errors.
For a full breakdown of your take-home pay, try our salary calculator.