Tax Over £100k: The 60% Tax Trap
How the Personal Allowance taper creates an effective 60% marginal tax rate between £100,000 and £125,140, and 5 ways to mitigate it.
In one sentence
Earning over £100,000 in the UK reduces your £12,570 Personal Allowance by £1 for every £2 of income, creating an effective 60% marginal Income Tax rate up to £125,140.
Quick answer
- Personal allowance tapers by £1 for every £2 of income over £100,000
- Creates an effective 60% Income Tax rate (62% with NI) between £100k and £125,140
- Triggers loss of Tax-Free Childcare and 15/30 hours free childcare eligibility
- Mitigated by pension salary sacrifice, Gift Aid, or dividend timing for directors
What happens when your income crosses £100,000 in the UK?
Crossing £100,000 in taxable income triggers one of the steepest tax steps in the UK tax system. For the 2026/27 tax year, your Personal Allowance (£12,570) is reduced by £1 for every £2 of adjusted net income you earn above £100,000.
By the time your adjusted net income reaches £125,140, your Personal Allowance is reduced to zero. This tapering mechanism creates an effective 60% marginal Income Tax rate on earnings between £100,000 and £125,140.
Why the math creates a 60% marginal tax rate
Many taxpayers expect to pay the 40% higher rate on income over £50,270. However, between £100,000 and £125,140, two tax effects happen at the exact same time:
- 40% Income Tax: You pay 40% tax directly on the extra £1 earned.
- 20% Lost Allowance Tax: Losing 50p of Personal Allowance exposes an extra 50p of income to 40% tax, adding an extra 20p of tax for every £1 earned.
Combined, you pay 60p in Income Tax on every £1 earned in that band. When you add 2% Class 1 National Insurance (for employees) or 2% Class 4 National Insurance (for sole traders), the combined deduction is 62%.
Worked example: salary increase from £100,000 to £110,000
| Income tier | Gross income | Personal allowance | Taxable income | Total Income Tax |
|---|---|---|---|---|
| At £100,000 | £100,000 | £12,570 | £87,430 | £22,432 |
| At £110,000 | £110,000 | £7,570 | £102,430 | £28,432 |
| Difference on extra £10k | +£10,000 | -£5,000 | +£15,000 | +£6,000 (60%) |
Note: Figures exclude National Insurance deductions and student loan repayments, which increase the total marginal deduction further.
Other hidden costs of crossing the £100,000 threshold
The 60% marginal tax rate is not the only financial penalty for earning over £100,000. Crossing £100,000 of adjusted net income also triggers the loss of valuable family benefits:
- Loss of Tax-Free Childcare: If either parent earns £100,000 or more in adjusted net income, both parents lose eligibility for Tax-Free Childcare (worth up to £2,000 per child per year).
- Loss of 15/30 hours free childcare: High-earning parents lose access to the government-funded childcare hours scheme. Earning £100,001 instead of £99,999 can cost a family thousands in lost childcare support.
- Self Assessment filing requirement: You must file a Self Assessment tax return if your adjusted net income exceeds £100,000, even if all your income is taxed under PAYE.
5 legitimate ways to mitigate the £100k tax trap
Because the taper is based on Adjusted Net Income (taxable income minus allowable deductions), you can reduce your income back below £100,000 using approved tax planning:
1. Salary sacrifice pension contributions
Paying extra salary directly into a workplace pension or SIPP reduces your adjusted net income pound-for-pound. A £10,000 pension contribution made between £100,000 and £110,000 effectively costs only £4,000 net, giving you 60% tax relief.
2. Gift Aid charitable donations
Donations to registered charities made under Gift Aid extend your basic-rate band and reduce your adjusted net income calculation, restoring lost Personal Allowance.
3. Dividend timing (Company Directors)
If you run your own limited company, you can defer dividend declarations or retain profits inside the business at Corporation Tax rates rather than drawing dividends that trigger the £100,000 Personal Allowance taper.
4. Non-cash employee benefits and electric vehicles
Structuring salary sacrifice for an electric company car (which carries a low Benefit-in-Kind rate) reduces gross salary for tax purposes while providing a vehicle.
5. Spouse shareholding and income splitting
For limited company owners, restructuring shares to allow a spouse who earns less to receive dividends can optimize the family tax position and preserve Personal Allowances.
Self Assessment filing obligations for high earners
HMRC monitors the £100,000 threshold through PAYE P60s and Self Assessment returns. If your income exceeds £100,000, you must ensure your tax code is updated or submit a Self Assessment return to calculate the exact allowance reduction.
Read our guide on UK tax thresholds for 2026/27 or see how our Self Assessment tax preparation service handles high-earner tax returns.
Earning near or over £100,000?
Book a 20-minute consultation with a senior UK tax accountant. We will review your adjusted net income, pension relief, and tax extraction plan to ensure you do not pay unnecessary tax.
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