How much do I need to contribute to get under £100,000?

Why £100,000 is the line

Two things happen at exactly £100,000 of adjusted net income, and neither of them is gentle.

• Your personal allowance starts disappearing. You lose £1 of allowance for every £2 of income above £100,000, and it is gone at £125,140 (gov.uk). Every pound in that band costs you 60p: 40p of tax, plus 20p of allowance destroyed.
• Tax-Free Childcare and the 30 funded hours stop. If you or your partner expects adjusted net income over £100,000, you are not eligible (gov.uk). That is a cliff, not a taper. One pound over and the lot goes.

For a parent with a child in nursery, that second one is frequently worth more than the tax. Thirty funded hours a week for 38 weeks is a serious sum in most of the country and an enormous one in London. It is entirely possible for a pay rise to leave a household worse off, which is a sentence that should not be true and is.

The formula, if you would rather do it yourself

Work out your adjusted net income, take £100,000 off it, and that is the gross contribution you need. What you hand over depends on your arrangement.

That 80% is HMRC's own gross-up rule in reverse: "for every £1 of pension contribution you made, take £1.25 from your net income" (gov.uk). So £8,000 out of your account reduces adjusted net income by £10,000.

If you are not sure which arrangement you are in, that is the more important question and I have written it up separately: does salary sacrifice reduce your adjusted net income?

The bonus problem

This is the version of the question I get most, usually in February, usually slightly too late.

A bonus is what tips most people over £100,000, and sacrificing a bonus is the cleanest fix there is. But a salary sacrifice has to be agreed before you become entitled to the money. It is a change to your employment contract, not a redirection of pay you have already earned. Once the bonus is awarded, that door is shut.

What is still open after the event is a personal contribution through relief at source, which reduces adjusted net income just as effectively. It costs you the National Insurance you would have saved, and you wait for part of the relief until your tax return is settled, but it works. So if you have missed the window, you have not missed the outcome.

If your employer runs bonus sacrifice, find out now when the election window opens. Put it in your calendar for the month before, not the month of.

What caps this

The annual allowance

£60,000 for 2026/27, covering your contributions and your employer's together, with the possibility of carrying forward unused allowance from the previous three tax years (gov.uk). For most people at £110,000 this is not binding. For someone with a large one-off bonus it very much can be.

The taper, if you earn a lot more

If your threshold income is over £200,000 and your adjusted income over £260,000, your annual allowance starts reducing. That is a separate calculation with its own definitions of income, and it is the point at which this stops being a thing to work out on the back of an envelope.

Minimum wage

Salary sacrifice cannot take your pay below the National Minimum Wage. Not a constraint at these income levels, but worth knowing the rule exists.

Whether you can actually spare it

The least discussed limit and usually the real one. Money in a pension is money you cannot touch until at least 57. The tax maths is excellent and it is still a decision about your life, not a spreadsheet exercise. If contributing the full gap leaves you without a cash buffer, contribute less and sleep better.

My honest take

The band between £100,000 and £125,140 is the most expensive stretch of income in the UK tax system, and almost nobody in it has been told. People find out when an accountant mentions it in passing, or when their childcare application is refused.

If you are in it, redirecting that slice into your pension before it is taxed is about as close to a free lunch as personal finance offers. Roughly 40p of take-home buys £1 in the pension, and if you have small children it also hands back childcare support worth thousands. The catch is that nothing happens automatically. You have to ask payroll, or fill in a form, or file a return.

Worth saying plainly: this is financial education, not regulated advice or a personal recommendation. The calculator uses 2026/27 rates for England, Wales and Northern Ireland. Scotland has its own income tax bands and the effective rate in the taper band there is higher. It assumes employment income only and ignores student loan repayments, which do not change adjusted net income but do change what reaches your bank account. Tax rules change and your circumstances are your own.