The £100k tax trap: why you're paying 60% and how to stop
There is a band of income in the UK tax system where your effective marginal tax rate is 60%. It applies to earnings between £100,000 and £125,140. Almost nobody outside this band knows it exists, and a significant number of people inside it don't realise it either.
It's called the personal allowance taper — and the good news is that it can be eliminated entirely with the right pension strategy.
For every £2 you earn above £100,000, you lose £1 of your personal allowance. By £125,140, your personal allowance has gone entirely. This creates an effective 60% marginal tax rate in that band. A pension contribution that brings your adjusted net income below £100,000 restores your allowance — and with it, up to £5,028 per year in tax savings.
If you are in Scotland: the taper mechanism is identical, but your effective rate in this band is 67.5% — not 60% — because Scotland's advanced rate is 45%. This also means the pension fix is worth more. See the Scotland section below.
How the taper works
Everyone in the UK gets a personal allowance — £12,570 of income on which you pay no tax. That allowance is supposed to be fixed. But there's a hidden rule: for every £2 of income above £100,000, HMRC withdraws £1 of your personal allowance.
The effect is that between £100,000 and £125,140, you're paying 40% income tax on the actual income, plus effectively paying 40% on the allowance being withdrawn — which together create a combined marginal rate of 60%.
| Income | Personal allowance remaining | Marginal rate in this band |
|---|---|---|
| Up to £100,000 | £12,570 (full) | 40% (higher rate) |
| £100,001 – £125,140 | Reducing to zero | 60% effective |
| Over £125,140 | £0 | 45% (additional rate) |
Note that the 45% additional rate above £125,140 is actually lower than the 60% rate in the taper zone. This means someone earning £120,000 is in a worse effective marginal tax position than someone earning £130,000 on the next pound of income.
The actual numbers at different incomes
The maximum personal allowance lost — and the maximum tax at stake — is the full allowance of £12,570 taxed at 40%, which equals £5,028. That's the additional tax bill someone earning £125,140+ pays versus someone earning £99,999. And it can be entirely avoided.
The pension fix
The same mechanism that eliminates the Child Benefit charge applies here. Your adjusted net income — the number HMRC uses for the personal allowance taper — is your gross income minus personal pension contributions and Gift Aid payments.
If you earn £115,000 and contribute £15,001 to a pension (personally or via salary sacrifice), your adjusted net income falls to £99,999. Your personal allowance is fully restored. You've also put £15,001 into a pension with 40% tax relief.
| Income | Contribution needed to get below £100k | Tax saving from restored allowance | Total pension tax relief |
|---|---|---|---|
| £105,000 | £5,001 | £2,000 | 40% on £5,001 = £2,000 + £2,000 allowance = £4,000 |
| £110,000 | £10,001 | £4,000 | 40% on £10,001 + restored allowance |
| £115,000 | £15,001 | £5,028 | ~60% effective rate on the contribution |
| £120,000 | £20,001 | £5,028 | Allowance fully restored |
| £125,140+ | £25,141+ | £5,028 | Allowance fully restored |
Neil's adjusted net income after salary sacrifice was £110,000. He was in the taper zone and effectively paying 60% on income between £100,000 and £110,000. He knew something felt wrong about his tax bill but hadn't identified exactly why.
After mapping the taper, Neil calculated he needed an additional £10,001 in pension contributions to bring his adjusted net income below £100,000. His employer's scheme allowed additional voluntary contributions via salary sacrifice. He increased contributions by £10,001/year.
The outcome: £5,028 in personal allowance restored, worth £2,011 in tax at 40%. Plus 40% relief on the £10,001 contribution itself (£4,000). Total tax benefit: approximately £6,011 on a contribution that cost him around £5,990 after relief — effectively getting pension contributions at no net cost.
Salary sacrifice vs personal contributions
Both mechanisms reduce your adjusted net income, but they work slightly differently:
- Salary sacrifice: Your contractual salary is reduced before it's reported to HMRC. Your adjusted net income is already lower. Also saves employee NI (8% on income in this band). Requires employer agreement.
- Personal pension contributions: You contribute from your post-tax pay, the pension provider adds 20% relief at source, and you claim additional higher-rate relief via Self Assessment. The contribution still reduces your adjusted net income for taper purposes.
For people in the £100k–£125k band, salary sacrifice is usually more efficient because it also saves NI. But if your employer's scheme doesn't offer salary sacrifice, personal contributions still achieve the core goal.
Gift Aid as a secondary lever
Charitable donations made through Gift Aid also reduce your adjusted net income for the taper calculation. If you give to charity regularly, make sure you're using Gift Aid — it extends your basic rate band and reduces your adjusted net income by the grossed-up value of your donation.
For larger donors, this can meaningfully contribute to getting adjusted net income below £100,000 alongside pension contributions. However, Gift Aid requires genuine charitable donations — it's not a tax planning mechanism on its own.
If you are in Scotland: the 67.5% trap
The taper mechanism works identically in Scotland — the same £100,000 threshold, the same £1 allowance lost per £2 earned, the same £125,140 ceiling. But the rate at which that withdrawn allowance is taxed is different, because Scotland's advanced rate band (45%) starts at £75,001 and runs through the entire taper zone.
In England and Wales, the taper zone costs you 60% on each pound of income — 40% higher rate tax, plus 20% from the withdrawn allowance also taxed at 40%. In Scotland, those same pounds cost you 67.5% — 45% advanced rate tax, plus 22.5% from the withdrawn allowance also taxed at 45%.
| England / Wales | Scotland | |
|---|---|---|
| Tax rate in taper zone | 40% (higher rate) | 45% (advanced rate) |
| Effective rate from withdrawn allowance | 20% | 22.5% |
| Combined effective income tax rate | 60% | 67.5% |
| With employee NI (2%) | 62% | 69.5% |
| With salary sacrifice NI saving | Up to 67% | Up to 71.5% |
| Value of restoring full personal allowance | £5,028 (at 40%) | £5,658 (at 45%) |
The pension fix works in exactly the same way — contributions reduce your adjusted net income — but the maths are even more compelling. A Scottish taxpayer earning £115,000 who contributes £15,001 to a pension saves the same allowance, but that restored allowance is worth £630 more in tax than it would be in England.
The relief at source problem
This catches a significant number of Scottish taxpayers and is almost never explained clearly. When you contribute to a personal pension or SIPP that operates on a relief at source basis, the pension provider automatically claims 20% basic rate tax relief from HMRC and adds it to your pot. That part happens automatically.
But if you are a Scottish advanced rate taxpayer (45%), your full entitlement is 45% relief — not 20%. The extra 25% does not come automatically. You must claim it yourself via your Self Assessment tax return. Many Scottish higher earners miss this entirely, leaving significant money unclaimed.
Relief at source (most personal pensions, SIPPs): 20% added automatically. If you pay 42% or 45% Scottish tax, you must claim the additional 22% or 25% via Self Assessment. If you have not been doing this, you can reclaim up to four years of unclaimed relief.
Gift Aid in Scotland
Gift Aid reduces your adjusted net income in exactly the same way as in England — the mechanism and the £100,000 taper threshold are identical. But the rate of relief you can personally reclaim is higher in Scotland.
When you make a Gift Aid donation, the charity claims 20% from HMRC automatically. As a Scottish advanced rate taxpayer (45%), you can then personally claim the additional 25% difference via Self Assessment — making your effective cost of a £100 gross donation just £55, compared to £60 for an England/Wales additional rate taxpayer. For larger regular donors, this meaningfully increases the efficiency of Gift Aid as a lever for reducing adjusted net income below £100,000.
Three actions to take now
- Calculate your adjusted net income. Gross salary minus existing pension contributions (if personal, not salary sacrifice) minus Gift Aid. If the result is between £100,000 and £125,140, you're in the taper zone.
- Work out the contribution needed to get below £100,000. This is adjusted net income minus £99,999. Make that contribution — either via salary sacrifice (more efficient) or personally into a SIPP or personal pension.
- Register for or maintain Self Assessment. If you earn above £100,000, HMRC requires you to file a Self Assessment return. Make sure you're registered, and use it to claim any additional pension relief owed on personal contributions.
Some people in this trap consider negotiating a lower salary to avoid the taper. This makes no sense financially — a pension contribution achieves the same tax result while building retirement wealth. The money goes into your pension, not out of your life entirely.