The Hidden 60% Tax Trap: What Personal Allowance Over 100k Really Means

Earn over £100,000 and you hit one of the least-loved parts of the UK tax system: your tax-free Personal Allowance starts tapering away. That means more of your income becomes taxable, even though nothing “new” has happened except you earning a bit more.

This is where pay rises can feel oddly unrewarding, because the maths in this band is brutal. If you’re anywhere near personal allowance over 100k, it’s worth understanding the taper and the straightforward ways people legally reduce the impact.

Personal allowance taper: The rule

This is the bit that turns “six figures” into “why does my payslip look offended?” Once your income goes over £100,000, your Personal Allowance doesn’t vanish in one go. It gets quietly nibbled away.

• The trigger: The taper starts when your adjusted net income goes over £100,000.
• The taper: You lose £1 of Personal Allowance for every £2 above £100,000.
• The endpoint: Your Personal Allowance becomes £0 at £125,140 of adjusted net income.
• The baseline: The standard Personal Allowance is £12,570 (so that’s the amount being tapered away).

📌 Pro Tip: Always sanity-check the rule on GOV.UK), but do your own quick test using adjusted net income, not “headline salary” — because pension contributions and Gift Aid can move that number.

Why it feels like 60%: The mechanics

In the £100,000–£125,140 range, extra income doesn’t just get taxed. It also drags some of your Personal Allowance out of hiding and into the tax net, so one pay rise can create two separate tax bites.

• What the taper does: for every extra £1 you earn over £100,000, you lose 50p of Personal Allowance, which means an extra 50p of income becomes taxable.
• Why that creates ~60%: if you’re paying 40% Income Tax on that slice, you pay 40p tax on the extra £1, plus 20p tax on the extra 50p that just became taxable, which totals 60p.
• Why take-home can feel even worse: if you’re employed and above the Upper Earnings Limit, there’s usually 2% employee National Insurance on top of Income Tax, which is how “60%” can feel closer to 62% in your bank account.

📌 Pro Tip: When you’re anywhere near this band, don’t evaluate a bonus or pay rise by the headline number — run the “£1 becomes £1.50 taxable” logic first, then decide if you want to reduce your adjusted net income instead of just absorbing the hit.

Who’s affected—and what counts as income

The Personal Allowance taper isn’t limited to one type of taxpayer. It applies to anyone whose adjusted net income goes over £100,000 — whether that income comes through PAYE, Self Assessment, or a mix of both.

• Who it can affect: Employees on PAYE, the self-employed, and anyone filing a Self Assessment tax return if their adjusted net income is above £100,000.
• What counts towards the threshold: HMRC looks at adjusted net income, which broadly includes salary, bonuses, taxable benefits in kind, dividends, rental income, and pension income, then subtracts certain reliefs such as pension contributions and Gift Aid.
• Across the UK: Scotland has different income tax bands and rates, but the taper principle still applies across the UK once adjusted net income goes over £100,000.

📌 Pro Tip: If you’re close to £100k, check your “extras” as well as salary — bonuses, benefits, dividends and rental profit often explain why someone tips into the taper unexpectedly.

Where it hits in the tax bands

The Personal Allowance taper doesn’t sit neatly inside one tax bracket. It cuts across bands, which is why it can feel like your tax rate is doing parkour.

• It increases your taxable income. Losing allowance means more of your income becomes taxable, which can push more of it into the higher-rate band even if your headline salary hasn’t changed much.
• It can turn “small” extra income into a big tax jump. Bonuses, a pay rise, or one-off income can land right in the taper zone and face a very high effective rate because you’re paying tax and losing allowance at the same time.
• It can affect how savings and dividends are taxed. Because the taper changes your taxable income and which band you sit in, it can reduce how much income is taxed at lower rates and increase the slice taxed at higher rates, which can mean a larger charge on interest or dividends outside wrappers.

📌 Pro Tip: If you’ve got control over timing, try not to stack everything into one tax year—spreading a bonus, dividends, or a share sale across years can keep more income out of the worst part of the taper.

Legal ways to reduce adjusted net income (and the pain)

The £100k trap is driven by adjusted net income, so the cleanest fixes are the ones that reduce that number using reliefs HMRC already recognises. Here are the main routes, in a consistent format.

• Pension route: Make personal contributions or use salary sacrifice to reduce adjusted net income and get Income Tax relief, while keeping an eye on the tapered annual allowance and whether carry forward is available from earlier tax years.
• Gift Aid route: Make Gift Aid donations to reduce adjusted net income and potentially extend your basic-rate band, then record the donations correctly on your tax return if needed.
• Timing route: Manage when income is recognised and when allowable costs land, where you have flexibility (common for the self-employed), to improve your position in the current tax year.
• Admin route: Confirm what your pension scheme/provider has processed and keep the paperwork, because relief only helps if it’s actually applied and reported correctly.

📌 Pro Tip: If you’re just over £100k, a relatively small pension contribution or Gift Aid donation can be unusually powerful here, because it can save tax in the band where the allowance is tapering away.

Reporting it right (and getting reliefs counted)

The relief only helps if HMRC actually sees it. Most “I still got stung” stories in the £100k band aren’t about the rules — they’re about the reporting.

• Self Assessment route: If you file a tax return, make sure pension contributions and Gift Aid are entered in the right places so HMRC calculates the correct amount of tax and higher-rate relief where applicable.
• PAYE-only route: If you don’t normally file, you can update details through your HMRC Personal Tax Account so your tax code reflects reliefs during the year, then HMRC reconciles everything through your end-of-year tax calculation.

📌 Pro Tip: After you report anything that changes adjusted net income, check your tax code a few weeks later. If it hasn’t moved, HMRC may not have applied it yet, and you don’t want to discover that in your P800.

Turn the £100k trap into a plan

The personal allowance over 100k taper isn’t a glitch. It’s the rule working exactly as written, which is why it feels so rude. But it’s also why it’s one of the few parts of the tax system where smart, legal planning can make a genuinely outsized difference. Reduce adjusted net income, get the reporting right, and you can keep more of your Personal Allowance and bring your tax bill back down to earth.

If you’re near this band and want to know which moves actually make sense for your situation, book a free financial review with a regulated adviser through Unbiased. They can run the numbers, sanity-check your options, and help you soften the hit.

Frequently Asked Questions (FAQ)