For many professionals, earning over £100,000 is seen as a major milestone. But in the UK tax system, crossing that line can create an unexpected problem: one where earning more does not necessarily mean taking home more.
Following the latest Budget, this issue has become even more pronounced. Quiet changes to salary sacrifice and continued frozen tax thresholds mean more people are being pulled into what is commonly known as the £100k tax trap.
(Reading Time: Approx. 4 minutes)
Topics Discussed:
- How the £100k tax trap works, including the 60% effective tax rate and loss of personal allowance
- The impact of recent Budget changes, including restrictions on salary sacrifice and what individuals can do to plan effectively
What is the £100k tax trap?
The £100k tax trap arises from the way the personal allowance is withdrawn once income exceeds £100,000.
Every UK taxpayer is entitled to a tax-free personal allowance of £12,570. However, once your adjusted net income goes above £100,000, this allowance is reduced by £1 for every £2 earned.
Allowance reduction: £¹⁄£₂ over £100,000
By the time your income reaches £125,140, your personal allowance is completely removed.
This creates an effective tax rate of 60% on income between £100,000 and £125,140 (around 62% including National Insurance). In Scotland, this can be even higher.
Why this matters in real terms
The impact is not just theoretical; it has very real financial consequences.
If an individual earning £100,000 receives a £10,000 bonus:
- £10,000 is taxed at 40%
- £5,000 of personal allowance is lost
- The remaining £5,000 becomes taxable at 40%, adding another £2,000
Total tax on the £10,000 bonus: £6,000
Effective tax rate: 60%
This means only £4,000 of the £10,000 bonus is actually retained.
Now layer in childcare.
If your adjusted net income exceeds £100,000, you can lose access to funded childcare hours and tax-free childcare entirely.
For many families, this is worth several thousand pounds per year. In some cases, earning slightly more can leave you materially worse off overall.
This is why the £100k threshold is often described as a “cliff edge”.
Why the problem is growing
This issue is becoming more widespread due to fiscal drag.
The £100,000 threshold has been frozen for years, while wages have increased. As a result, more individuals, including professionals who would not traditionally consider themselves “high earners”, are being pulled into this band.
At the same time:
- student loan repayments are rising
- childcare costs remain high
- tax thresholds are not keeping pace with inflation
The combined effect is that the £90,000 to £125,000 range has become a financial “danger zone”.
What has changed in the latest Budget?
Historically, one of the most effective ways to manage this issue was through salary sacrifice, particularly by diverting income into pension contributions.
This allowed individuals to:
- reduce their adjusted net income below £100,000
- retain their personal allowance
- preserve childcare benefits
- save National Insurance at the same time
However, the latest Budget has introduced a significant change.
From April 2029:
- only the first £2,000 of salary sacrifice will avoid National Insurance
- 3amounts above £2,000 will still reduce adjusted net income (helping with childcare eligibility)
- but they will no longer generate National Insurance savings
In practical terms, this means:
- salary sacrifice becomes less efficient
- take-home pay reduces compared to the current system
- one of the key “escape routes” from the £100k trap is being restricted
The system has not just tightened; it has fundamentally shifted.
How to manage the £100k tax trap
If your income is approaching or within this range, proactive planning is essential.
Key strategies include:
Treat £100,000 to £125,000 as a critical planning band
This is where marginal tax rates spike and benefits begin to taper or disappear.
Use pension contributions strategically
Pension contributions remain one of the most effective ways to reduce adjusted net income and restore your personal allowance. While salary sacrifice rules are changing, contributions still provide significant tax relief.
Consider charitable donations
Gift Aid donations extend your tax bands and reduce adjusted net income, helping to preserve your personal allowance.
Plan bonuses and timing of income
Where possible, spreading or deferring income across tax years can help avoid breaching the threshold in a single year.
Monitor childcare eligibility closely
A small increase in income can result in a disproportionate loss of support. This should be reviewed annually.
Focus on net income, not headline salary
Decisions should be based on what you actually retain, not just what you earn.
Summary
In summary, earning over £100,000 can leave you worse off, not better.
Between £100,000 and £125,140, the loss of your personal allowance creates an effective tax rate of around 60%, and even higher if childcare support is lost.
Recent Budget changes have made this more restrictive by limiting the benefits of salary sacrifice, while frozen tax bands are pulling more people into this range.
The key takeaway is to treat £100,000 to £125,000 as a critical planning zone.
Always focus on your take-home pay rather than your headline salary, and plan carefully around bonuses, pay rises, and pension contributions, as even small increases in income can have a significant financial impact.
Get in touch with us to ensure you are structuring your income in the most tax-efficient way possible.
Fill out our form here for any questions, email us at info@taxexpert.co.uk, or message us on our WhatsApp for out of office hours.
Kind regards,
Ilyas Patel
