The £100k Tax Trap Explained: Why You Pay 60% Tax
All tax calculations in this guide use 2025/26 tax year rates and thresholds.
Earning £100,000 sounds like a milestone worth celebrating. But in the UK tax system, it's actually the start of one of the harshest traps: a 60% marginal tax rate, lost childcare support, and potential tax bills that mean earning more can leave you with less.
This guide explains exactly what happens when you cross £100k, how much it really costs, and practical strategies to escape the trap legally.
A Growing Problem: More Workers Every Year
The £100k tax trap isn't some niche concern for the ultra-wealthy. Thanks to frozen tax thresholds and wage inflation, it's catching more ordinary professionals every year:
| Tax Year | Workers Over £100k | In the 60% Trap (£100k-£125k) |
|---|---|---|
| 2017/18 | ~1.1 million | ~300,000 |
| 2025/26 | 1.95 million | ~725,000 |
| 2026/27 (projected) | 2.06 million | ~780,000 |
| 2029/30 (projected) | 2.3 million | ~900,000 |
That's over 2 million workers—roughly 6% of the UK workforce—now earning above £100k. The number caught in the brutal 60% band between £100k and £125k has more than doubled since 2017.
Why the surge? The £100k threshold has been frozen since 2010. Meanwhile, salaries have risen with inflation. Jobs that paid £75k a decade ago now pay £100k+. Senior developers, experienced nurses, headteachers, train drivers, and countless other professionals are being dragged into a tax trap originally designed for "high earners."
HMRC projects 3.1 million workers will earn over £100k by 2035. That's nearly 1 in 10 of the workforce. If you're not in the trap yet, you might be soon—especially if you're on a career trajectory with regular pay rises or promotions.
What Is the £100k Tax Trap?
The £100k tax trap is actually multiple traps bundled together, all triggered when your adjusted net income exceeds £100,000:
| Trap | How It Works | Maximum Cost |
|---|---|---|
| Personal Allowance Taper | Lose £1 of allowance for every £2 earned over £100k | £5,028 extra tax |
| 60% Marginal Rate | Effective 60% tax on income between £100k-£125,140 | £15,084 tax on £25,140 |
| Tax-Free Childcare | Lost entirely (cliff edge) | £2,000 per child |
| 30 Hours Free Childcare | Lost entirely (cliff edge) | ~£8,000 per child |
For a family with two young children, crossing £100k could cost over £25,000 per year in extra tax and lost benefits. That's why understanding and managing this threshold is crucial.
The 60% Tax Rate: How It Works
The UK doesn't have an official 60% tax band. But when you combine the 40% higher rate with the loss of personal allowance, the effective rate between £100,000 and £125,140 is exactly 60%.
To put this in perspective: someone earning £110,000 pays a higher marginal rate than someone earning £500,000. The person on half a million pays 45%. The person on £110k effectively pays 60-62%. It's one of the strangest quirks in the UK tax system.
The Maths Behind 60%
For every £2 you earn above £100,000, you lose £1 of your £12,570 personal allowance. This lost allowance is then taxed at 40%, adding an extra 20% to your tax bill:
- Base higher rate: 40%
- Plus: (50% × 40%) for lost allowance = 20%
- Total effective rate: 60%
This continues until your personal allowance is completely eliminated at £125,140 (£100,000 + 2 × £12,570). Above £125,140, you pay the standard 45% additional rate—ironically lower than the 60% effective rate just below it.
Scenario: You earn £105,000 and receive a £1,000 pay rise
What happens:
- Standard 40% tax on £1,000: £400
- Lost personal allowance: £500 (£1,000 ÷ 2)
- Tax on lost allowance at 40%: £200
- National Insurance at 2%: £20
Total deductions: £620
You keep: £380 from your £1,000 raise
That's an effective 62% marginal rate (including NI).
The 60% rate only considers income tax. Add 2% National Insurance on earnings above £50,270, and the true marginal rate in the £100k-£125k band is 62%. Every £1,000 raise only puts £380 in your pocket.
The Childcare Cliff Edge
While the personal allowance tapers gradually, childcare benefits have a brutal cliff edge. At £99,999 you get full support. At £100,001 you get nothing.
This is where the £100k trap becomes genuinely life-changing for families. A £1 pay rise can cost you £10,000+ in childcare support. It's not an exaggeration—it's the maths.
What You Lose
From September 2025, eligible working parents can receive up to 30 hours of free childcare per week from when their child is 9 months old until they start school (typically the September after they turn 4). Combined with Tax-Free Childcare, the total value per child can exceed £10,000 per year.
| Benefit | Who Gets It | Annual Value |
|---|---|---|
| Tax-Free Childcare | Children under 12 | Up to £2,000 per child |
| 30 Hours Free (9m-school) | Working parents, child 9 months to school age | ~£8,000 per child |
| Total per child | Up to £10,000 |
Note: The universal 15 hours for 3-4 year olds has no income test—every family gets this regardless of income. But the working parent entitlements (30 hours, Tax-Free Childcare) are lost entirely above £100k.
If either parent has adjusted net income over £100,000, the whole family loses eligibility. It doesn't matter if the other parent earns £30,000—one parent over the threshold means no support for anyone.
Scenario: Couple with 2 children (ages 1 and 3)
Parent A: £105,000 salary
Parent B: £45,000 salary
What they lose by Parent A being over £100k:
- Personal allowance taper: ~£2,000 extra tax
- Tax-Free Childcare: £4,000 (£2,000 × 2 children)
- 30 hours free childcare: ~£16,000 (£8,000 × 2 children)
Total annual cost: ~£22,000
To replace this through extra earnings at a 60% effective rate, they'd need roughly £55,000 more gross income. The £5,000 that pushed them over £100k is costing them over four times that amount.
Understanding Adjusted Net Income
Both the personal allowance taper and childcare eligibility use adjusted net income (ANI) as the threshold—not your gross salary. This is crucial because ANI can be reduced, potentially keeping you under £100k even with a higher gross salary.
How ANI Is Calculated
Start with your total taxable income, then subtract:
- Pension contributions (personal contributions or salary sacrifice)
- Gift Aid donations (grossed up by 25%)
- Trading losses (if self-employed)
The result is your adjusted net income. Keep this under £100,000 and you avoid both the 60% tax band and the childcare cliff edge.
Gross salary: £115,000
Pension contribution (salary sacrifice): £12,000
Gift Aid donations: £2,400 (grossed up to £3,000)
Adjusted Net Income:
£115,000 - £12,000 - £3,000 = £100,000
Despite a £115,000 salary, this person's ANI is exactly £100,000—keeping them just under the threshold and preserving their personal allowance and childcare eligibility.
Strategy 1: Pension Contributions
The most powerful and common strategy for escaping the £100k trap is increasing pension contributions. Every pound contributed reduces your ANI by a pound.
This isn't "losing" money—it's redirecting it from HMRC to your future self. At 60%+ effective tax rates, pension contributions are extraordinarily efficient. You're essentially getting a guaranteed 150%+ return on your contribution through tax savings alone (before any investment growth).
Salary Sacrifice vs Personal Contributions
Salary sacrifice is the most tax-efficient method if your employer offers it:
- Reduces gross salary before tax and NI are calculated
- Saves both income tax (40-60%) AND National Insurance (2%)
- Reduces ANI pound-for-pound
- Employer also saves 13.8% employer NI (sometimes shared with you)
Personal contributions (relief at source) work too:
- You pay from net salary, provider claims 20% basic rate from HMRC
- Claim additional 20-40% relief through self-assessment
- Still reduces ANI by the gross contribution amount
- No National Insurance saving
Starting position: £108,000 salary, 2 children in nursery
Without planning:
- Personal allowance lost: £4,000 → extra tax £1,600
- Tax-Free Childcare lost: £4,000
- 30 hours free childcare lost: ~£16,000
- Total cost: ~£21,600
With £9,000 salary sacrifice pension:
- New ANI: £99,000
- Personal allowance: Fully restored
- Childcare: Fully eligible
- Pension pot increase: £9,000
What the £9,000 pension actually costs you:
- Gross reduction: £9,000
- Tax saved (60% effective rate): £5,400
- NI saved (2%): £180
- Net cost to take-home: £3,420
Result: £3,420 less in your bank account, but £9,000 more in your pension, plus £21,600 in preserved benefits. A clear win.
The November 2025 Budget announced that from April 2028, the NI saving on salary sacrifice pension contributions may be capped. The income tax relief and ANI reduction will remain, but plan for reduced NI benefits from 2028 onwards.
Pension Annual Allowance
You can contribute up to £60,000 per year to pensions with tax relief (or 100% of earnings if lower). If you haven't used your full allowance in previous years, you can carry forward unused amounts from the last 3 tax years.
This makes pensions particularly powerful for one-off income spikes like bonuses or RSU vests—you may have significant carry-forward available.
Strategy 2: Gift Aid Donations
Charitable donations through Gift Aid also reduce your adjusted net income. The donation is "grossed up" by 25%, so an £800 donation counts as £1,000 reduction in ANI.
Situation: ANI of £102,400 (£2,400 over threshold)
Gift Aid donation needed: £1,920 (grossed up to £2,400)
What happens:
- You donate £1,920 to charity
- Charity claims £480 from HMRC (25% gross-up)
- Total charitable benefit: £2,400
- Your ANI reduces by £2,400 to exactly £100,000
- You claim 20% additional relief through self-assessment: £480
Net cost of donation: £1,440 (£1,920 - £480 claimed back)
Plus you preserve your personal allowance and childcare eligibility.
This strategy works best if you're already planning charitable giving. It's not worth donating just for the tax benefit, but if you support charities anyway, timing donations strategically can help.
Strategy 3: Timing Income
If you have control over when you receive income (bonuses, dividends, contractor payments), timing can help manage which tax year the income falls in.
Deferring Bonuses
Some employers allow bonus deferral. If a bonus would push you over £100k, deferring to the next tax year might keep you under the threshold in both years (depending on your base salary).
Contractor Income
If you run a limited company, you have flexibility over salary and dividend timing. Spreading income across tax years can help avoid the £100k spike in any single year.
While timing is legitimate, artificial arrangements purely to avoid tax may fall foul of HMRC's anti-avoidance rules. Take professional advice if structuring complex arrangements.
Strategy 4: Childcare Timing
Childcare eligibility is assessed quarterly when you reconfirm. If you know a spike is coming (bonus, RSU vest), understanding the assessment periods can help:
- You reconfirm every 3 months to maintain eligibility
- A temporary spike over £100k may only affect one quarter
- Plan pension contributions to offset known spikes before reconfirmation
If you go over £100k in one quarter but are back under the next, you can reapply. There's typically a grace period, but don't rely on this—proactive planning is better.
Who Gets Caught in the Trap?
The £100k trap used to be a concern for City bankers and corporate executives. Now it's catching a much wider range of professions:
Tech Workers
Senior developers, engineering managers, and product leads now routinely earn £100k+ base salaries in London and increasingly elsewhere. Add RSUs or bonuses and the numbers climb further. See our RSU Tax Trap guide for stock-specific planning.
NHS Consultants and Senior Doctors
Consultant salaries plus private practice income frequently crosses £100k. The NHS pension adds complexity with tapered annual allowance rules on top.
Headteachers and Senior Educators
Large secondary school heads and academy principals often earn £100k+. The salary bands have risen while the threshold hasn't.
Experienced Train Drivers
With overtime and unsocial hours payments, experienced drivers at some operators now exceed £100k. Ongoing pay settlements continue to push typical salaries higher.
Senior Solicitors and Accountants
Partners and senior associates in professional services routinely earn in the trap range, especially in London and major cities.
Couples Where One Partner Gets a Promotion
A promotion pushing one partner over £100k affects the whole family's childcare eligibility, even if the other partner's income is modest.
Common Mistakes
1. Not Knowing Your ANI
Many people focus on gross salary without calculating adjusted net income. If you don't know your ANI, you can't plan effectively. Use our calculator to check your current position.
2. Forgetting Variable Income
Bonuses, RSUs, overtime, rental income—all count towards ANI. A surprise vest or bonus can push you over unexpectedly if you're not tracking everything.
3. Reacting Too Late
Pension contributions must be made in the same tax year as the income. If your RSUs vest in March and you don't act until June, it's too late for that tax year.
4. Ignoring Partner's Income
For childcare, only one parent needs to exceed £100k to lose eligibility. Both partners need to track their ANI, not just the higher earner.
5. Assuming Next Year Will Be Different
If you're over £100k this year, you'll probably be over next year too unless something changes. Build permanent pension contributions into your budget rather than treating it as a one-off fix.
Should You Avoid Going Over £100k?
Not necessarily. The right decision depends on your circumstances:
When Staying Under Makes Sense
- You have young children in childcare (the cliff edge is brutal)
- You're only slightly over £100k (easy to offset with pension)
- You want to maximise retirement savings anyway
- The "lost" money goes into your pension, not disappeared
When Going Over Might Be Fine
- No children or children already in school (no childcare to lose)
- You're significantly over £100k and can't contribute enough to pension
- You've hit pension annual allowance limits
- You prefer cash now over pension later
The key is making an informed choice rather than drifting over £100k without realising the consequences.
Quick Decision Guide
| Your Situation | Recommended Action |
|---|---|
| ANI £100k-£125k, have young children | Maximise salary sacrifice pension to get ANI under £100k |
| ANI £100k-£125k, no children | Consider pension to escape 60% band, but less urgent |
| ANI significantly over £125k | Personal allowance fully gone; focus on other tax planning |
| Variable income (bonuses/RSUs) | Model scenarios, plan pension contributions around spike dates |
| Self-employed/contractor | Consider income timing and company pension contributions |
How Our Calculator Helps
Our tax calculator automatically identifies when you're approaching or in the £100k trap and shows you:
- Your current adjusted net income
- How much personal allowance you're losing
- Your effective marginal tax rate
- Childcare benefits at risk
- Optimal pension contribution to escape the trap
- Net benefit of making additional pension contributions
Enter your income details, pension contributions, and family situation to see your personalised analysis.
Key Takeaways
- Over 2 million UK workers now earn above £100k—and the number is growing every year
- The £100k trap creates an effective 60% tax rate between £100,000 and £125,140
- You lose £1 of personal allowance for every £2 earned above £100k
- Childcare benefits (Tax-Free Childcare, 30 hours) are lost entirely above £100k—no taper
- If either parent exceeds £100k, the whole family loses childcare eligibility
- Pension contributions reduce your adjusted net income and can keep you under £100k
- Salary sacrifice pensions are most efficient (save NI too), though this may change from 2028
- Contributions must be made in the same tax year as the income
- Plan ahead—know your vesting dates, bonus timing, and reconfirmation periods
- For families with young children, the total cost of crossing £100k can exceed £20,000/year
Official Resources
- Gov.uk: Income Tax rates and bands
- HMRC: Adjusted Net Income
- Gov.uk: Pension Annual Allowance
- Childcare Choices
Disclaimer
This article is for general information only and is not financial, tax, or legal advice. Rules can change and your circumstances matter. If you're unsure, consider speaking to a regulated adviser or accountant.