UK Income Tax Explained 2026: Complete Guide for Employees and Expats
By Paulo Horta · Updated March 2026 · 12 min read
The UK tax system has a reputation for complexity — and in some areas, that reputation is deserved. But for most employees, the fundamentals are straightforward once you understand the structure. This guide explains exactly how UK income tax and National Insurance work in 2026, including the traps that catch high earners off guard, how to use the system's legitimate planning tools, and what changes for non-UK nationals moving to London for work.
The Basic Structure: How UK Income Tax Works
UK income tax is collected through a system called PAYE — Pay As You Earn. Your employer deducts income tax and National Insurance directly from your salary before it reaches your bank account. You never see the gross amount — it is calculated, deducted, and paid to HMRC automatically each month.
This is fundamentally different from systems like France or Germany, where you receive your gross salary and pay tax separately. Under PAYE, the number you negotiate with your employer is your gross salary, but the number that matters for your lifestyle is your net take-home — which can be substantially lower.
The Personal Allowance
Every UK taxpayer receives a Personal Allowance — an amount of income completely free of income tax. For 2025/26, the Personal Allowance is £12,570. This means the first £12,570 of your annual income attracts zero income tax. Above this threshold, tax is charged at progressive rates.
The Three Income Tax Bands
| Income Band | Tax Rate | Annual Threshold |
|---|---|---|
| Personal Allowance | 0% | Up to £12,570 |
| Basic Rate | 20% | £12,571 – £50,270 |
| Higher Rate | 40% | £50,271 – £125,140 |
| Additional Rate | 45% | Above £125,140 |
Example — £60,000 salary:
- First £12,570: 0%
- £12,571 to £50,270 at 20%: £7,540
- £50,271 to £60,000 at 40%: £3,892
- Total income tax: £11,432
Note: Scotland has its own income tax rates, which differ from the rest of the UK on income between £25,689 and £43,662.
National Insurance: The Hidden Tax
National Insurance Contributions (NICs) are a separate levy that funds the state pension, NHS, and other social benefits. For employees in 2025/26:
- 0% on earnings up to £12,570/year
- 8% on earnings between £12,570 and £50,270/year
- 2% on earnings above £50,270/year
National Insurance is often described as a second income tax because it functions identically to income tax in terms of how it reduces take-home pay. The key difference is that NICs do not apply to dividends, rental income, or pension income — which creates planning opportunities for those with multiple income sources.
The £100,000 Tax Trap
One of the most important — and most frequently misunderstood — features of the UK tax system is the Personal Allowance taper.
At incomes above £100,000, the £12,570 Personal Allowance is progressively withdrawn. For every £2 of income above £100,000, £1 of Personal Allowance is lost. The allowance is fully eliminated at £125,140.
Between £100,000 and £125,140, each additional pound of income costs 40p in income tax plus 20p of lost tax relief on the withdrawn personal allowance — an effective marginal rate of 60%.
A professional who receives a pay rise from £99,000 to £110,000 may see their take-home pay increase by far less than expected.
How to mitigate the £100,000 trap: Pension contributions reduce your "adjusted net income" — the figure used to calculate the Personal Allowance taper. By contributing to a pension, you can bring your adjusted net income back below £100,000 and restore your full Personal Allowance. A professional earning £115,000 who contributes £15,000 to their pension reduces their adjusted net income to £100,000, restoring their full allowance and effectively receiving 60% tax relief on those contributions.
National Insurance for High Earners
The effective marginal rates at different income levels:
- £12,570 to £50,270: 20% income tax + 8% NICs = 28% marginal rate
- £50,270 to £100,000: 40% income tax + 2% NICs = 42% marginal rate
- £100,000 to £125,140: effective 60% income tax + 2% NICs = 62% marginal rate
- Above £125,140: 45% income tax + 2% NICs = 47% marginal rate
The ISA: The UK's Most Powerful Savings Tool
Each UK taxpayer can contribute up to £20,000 per tax year into an ISA (Individual Savings Account), and all growth, income, and withdrawals are completely free of UK tax — forever.
Types of ISA:
Stocks and Shares ISA: Invest in equities, funds, and bonds within a tax-free wrapper. Ideal for long-term wealth building.
Cash ISA: A savings account within the ISA wrapper. All interest is tax-free.
Lifetime ISA (LISA): Available for those aged 18–39. Contributions of up to £4,000/year receive a 25% government bonus (up to £1,000/year). Can be used to buy a first home or accessed from age 60.
For a professional earning above the higher rate threshold, the ISA removes the 40% tax on investment returns that would otherwise apply. Over a working career in London, maximising ISA contributions is one of the highest-return financial decisions available.
Pension Contributions and Tax Relief
UK pension contributions receive tax relief at your marginal rate — making them particularly valuable for higher and additional rate taxpayers.
Annual Allowance: You can contribute up to £60,000 per year into UK pension schemes (or 100% of your earnings if lower) and receive tax relief.
How relief works:
- Basic rate taxpayer (20%): £800 net contribution becomes £1,000 in your pension
- Higher rate taxpayer (40%): £600 net contribution becomes £1,000 (extra 20% claimed via self-assessment)
- Additional rate taxpayer (45%): £550 net contribution becomes £1,000
A 40% taxpayer who maximises pension contributions is effectively receiving a 67% return on their net contribution before any investment growth.
Self-Assessment: Do You Need to File a Tax Return?
Most UK employees have their tax handled entirely through PAYE and never need to file a self-assessment return. However, you must register for self-assessment if:
- Your income exceeds £100,000
- You have income from self-employment, rental properties, or investments
- You receive income from abroad
- You have capital gains above the annual exempt amount (£3,000 in 2024/25)
- You need to claim higher rate relief on pension contributions
Self-assessment returns for 2025/26 must be filed online by 31 January 2027. Late filing incurs an automatic £100 penalty.
Non-UK Nationals Moving to London
The Foreign Income and Gains (FIG) Regime
From April 2025, the previous non-dom remittance basis was replaced with the new Foreign Income and Gains (FIG) regime. Under FIG, individuals who become UK tax resident after a period of non-UK residency can elect to exempt their foreign income and gains from UK tax for the first four tax years of UK residence. After four years, worldwide income is subject to standard UK tax rates.
If you are moving to London from abroad for the first time (or returning after at least 10 years of non-UK residence), take advice on whether the FIG election is beneficial for your specific circumstances.
Split Year Treatment
In the tax year you arrive in the UK, you may be entitled to split year treatment — meaning you are treated as UK resident only from the date of your arrival, rather than for the full April–April tax year. This can significantly reduce your UK tax liability in your first year. Split year treatment must be claimed on your self-assessment return.
Effective Tax Rates: What You Actually Keep
| Gross Salary | Income Tax | NICs | Net Salary | Effective Rate |
|---|---|---|---|---|
| £30,000 | £3,486 | £1,394 | £25,120 | 16.3% |
| £50,000 | £7,486 | £3,034 | £39,480 | 21.0% |
| £60,000 | £11,432 | £3,234 | £45,334 | 24.4% |
| £80,000 | £19,432 | £3,634 | £56,934 | 28.8% |
| £100,000 | £27,432 | £4,034 | £68,534 | 31.5% |
| £120,000 | £40,225 | £4,234 | £75,541 | 37.1% |
| £150,000 | £52,460 | £4,634 | £92,906 | 38.1% |
Note: The effective rate at £120,000 is disproportionately high due to the Personal Allowance taper — demonstrating why pension contributions between £100,000 and £125,140 are so valuable.
Summary
The UK tax system is progressive and becomes increasingly complex at higher income levels. For most employees earning below £100,000, PAYE handles everything automatically and the effective tax rate is manageable. For higher earners, understanding the £100,000 Personal Allowance trap, maximising pension contributions, and using the ISA allowance are the three most impactful financial decisions available. Non-UK nationals moving to London should investigate the new Foreign Income and Gains regime and split year treatment before their first UK tax year begins — these elections cannot be made retrospectively.