Does salary sacrifice reduce your adjusted net income?

Short answer: yes. Under salary sacrifice the money never becomes your pay, so your adjusted net income falls by the full amount sacrificed and there is nothing to claim. The complication is that there are three ways to pay into a workplace pension, they behave differently, and people mix them up constantly. At £100,000 that mistake is expensive.

I spent six years in accountancy and four as a financial adviser, and I have read a great many payslips. This is the single thing people get wrong most often, and it is nearly always because nobody ever told them which arrangement they were in.

Why adjusted net income matters at all

Adjusted net income is not your salary. It is a specific HMRC measure, and it is the figure two important things are tested against.

• The personal allowance taper. Above £100,000 you lose £1 of personal allowance for every £2 of adjusted net income, and it is gone entirely at £125,140 (gov.uk). That is what creates the 60% effective rate.
• Tax-Free Childcare and the 30 funded hours. These stop if you or your partner has adjusted net income over £100,000 (gov.uk). No taper, no easing in. A cliff edge.

So the question is not academic. If you think you are under £100,000 and you are not, you can lose thousands of pounds of childcare support on top of the tax.

The three arrangements, and what each does

Here is the whole thing in one table. The rest of the article is just this, explained.

That gross-up is not my rule of thumb. HMRC's own guidance on adjusted net income puts it plainly: "for every £1 of pension contribution you made, take £1.25 from your net income" (gov.uk). Gift Aid donations work the same way.

Salary sacrifice

You agree to a lower salary, and your employer pays the difference into your pension. Because you never earn the money, it is not income, so it is not in adjusted net income either. Your P60 will show the lower figure.

This is the only one of the three that also saves National Insurance. Above the upper earnings limit of £50,270 employee National Insurance is 2%, and employer National Insurance is 15% (gov.uk). Some employers pass their saving on to you as well, which makes sacrifice meaningfully better than the alternatives. Ask yours. Many do and never mention it.

Net pay arrangement

Your contribution comes out of your gross pay before income tax is calculated. You get full relief immediately, at whatever rate you pay, with no claim to make. Your taxable pay on your payslip is lower than your gross pay by exactly the contribution.

Because the money has already come out before tax, it is captured at step one of the adjusted net income calculation. Do not deduct it again. Double-counting here is the most common error I see, and it makes people think they are further below £100,000 than they are.

Note that National Insurance is still worked out on your pay before the pension deduction, so there is no National Insurance saving here.

Relief at source

You pay from your take-home, and your pension provider claims 20% back from HMRC and adds it to your pot. Pay £800 and £1,000 lands.

Your taxable pay is not reduced, so nothing has happened yet as far as your tax code is concerned. You deduct the grossed-up £1,000 when working out adjusted net income, and you claim the rest of the relief through self assessment. If you are a higher or additional rate taxpayer on relief at source and you have never filled in a tax return, there is a good chance you are owed money. You can usually go back four tax years.

How to tell which one you have

Your payslip answers this in about ten seconds once you know what you are looking at.

• Gross pay itself looks low, and the pension line either does not appear as your deduction or is labelled as an employer contribution: salary sacrifice.
• Pension deduction sits above the tax line, and taxable pay is lower than gross pay: net pay arrangement.
• Pension deduction sits below the tax line, and taxable pay equals gross pay: relief at source.

If your payslip is one of the vague ones, email payroll and ask directly: "is our pension scheme salary sacrifice, net pay, or relief at source?" They answer that question every week. It is not a strange thing to ask.

A worked example on £110,000

Say your only income is a salary of £110,000 and you want to bring adjusted net income down to £100,000. That means a gross contribution of £10,000 whichever route you take. What differs is what it costs you.

Here is the arithmetic, so you can check it rather than take my word for it. At £110,000 your personal allowance has tapered to £7,570, leaving taxable income of £102,430 and income tax of £33,432. At £100,000 the full £12,570 allowance survives, taxable income is £87,430 and the tax is £27,432. The difference is £6,000 on £10,000 of income, which is the 60% rate people talk about: 40p of tax on the pound, plus another 20p because every £2 of income destroys £1 of allowance that was sheltering income from 40% tax.

Read the bottom row twice. Under £4,000 of take-home puts £10,000 into your pension, and restores your personal allowance, and puts you back under the childcare line. There is no investment anywhere that does that. It is simply what happens when income in the 60% band is redirected before it is taxed.

The relief-at-source column is worth a second look too. You hand over £8,000 and only get the other £4,000 back when your tax return is settled. Same destination, very different cashflow, and worth planning for if the numbers are large.

Four things that catch people out

Sacrifice has to be agreed before you earn the money

A salary sacrifice is a change to your employment contract. You generally cannot sacrifice pay you have already become entitled to. In practice this means a February bonus needs the paperwork done before the bonus is awarded, not after it lands. Every year I talk to someone who found this out a fortnight too late.

The annual allowance is a ceiling on all of this

The annual allowance is £60,000 for 2026/27, covering your contributions and your employer's, and you may be able to carry forward unused allowance from the previous three tax years (gov.uk). If your threshold income is over £200,000 and your adjusted income over £260,000, your allowance tapers down, which is a different calculation and a different conversation.

Sacrifice cannot take you below the minimum wage

Your employer is not allowed to let sacrifice reduce your pay below the National Minimum Wage. Not a constraint at £110,000, but it matters for anyone using sacrifice aggressively on a modest salary.

Watch your tax code on relief at source

When HMRC learns about regular relief-at-source contributions, it often adjusts your tax code to give the higher-rate relief through payroll. That is helpful, but if the contribution then changes and the code does not, you can end up having had relief twice and owing it back. Check your coding notice when it arrives rather than filing it.

My honest take

If your employer offers salary sacrifice, use it. It is better than the alternatives by the National Insurance, and better again if they pass on their own saving. If they do not offer it, ask. Employers save money on it too, which makes it one of the easier things to get a yes to.

And if you are anywhere near £100,000, work out your actual adjusted net income properly, once, rather than assuming. The difference between thinking you are at £99,000 and actually being at £104,000 is a lost personal allowance and, if you have young children, thousands of pounds of childcare support.

Worth saying plainly: this is financial education, not regulated advice or a personal recommendation. Figures are for the 2026/27 tax year and apply to England, Wales and Northern Ireland. Scotland has its own income tax bands, so the effective rate in the taper band there is higher. Tax rules change and your circumstances are your own.