Salary sacrifice is usually written up as free money, and the first half of that is fair — it is the only pension arrangement that saves National Insurance as well as income tax. The second half of the story gets told much less often, which is that it works by making your salary genuinely smaller, and your salary is the number a surprising amount of other things are calculated from.
The short version: you gain National Insurance you would otherwise pay, and the gain is bigger for middle earners than for high earners. You give up gross salary, which is what mortgage lenders, statutory parental pay, death-in-service cover and redundancy pay are all measured against. Neither half of that makes it a good or bad idea — it makes it a trade-off worth understanding before you tick the box.
See the numbers on your own salary. Our free pension tax relief calculator has a salary sacrifice setting and shows the National Insurance saved alongside the tax relief, so you can compare it directly against the other two arrangements.
How it actually works
You agree with your employer to give up part of your contractual salary. In exchange, they pay that amount into your pension as an employer contribution. Your gross pay falls by the amount sacrificed, and because income tax and National Insurance are both calculated on gross pay, you pay less of both.
That is the whole mechanism, and the word doing the work is contractual. This is a change to your employment contract, not a payroll setting. The money never counts as your earnings, which is precisely why no National Insurance is due on it — and precisely why it disappears from every other calculation that starts with your earnings.
Compare that with the alternatives. Under a net pay arrangement your contribution also comes off before income tax, but your gross salary is untouched, so National Insurance is still charged on the full amount. Under relief at source you pay from taxed income and reclaim. We set all three out side by side in relief at source vs net pay.
What you gain
Employee National Insurance is charged at 8% on earnings between the primary threshold and the upper earnings limit of £50,270, and at 2% above that. Because sacrifice reduces your earnings from the top down, the rate you save depends on where your salary sits — and this produces a result most people find backwards.
| Salary | NI saved by sacrificing £3,000 | Net cost of the same £3,000 |
|---|---|---|
| £30,000 | £240 | £2,160 |
| £40,000 | £240 | £2,160 |
| £50,000 | £240 | £2,160 |
| £60,000 | £60 | £1,740 |
| £90,000 | £60 | £1,740 |
2026/27 rates, rest of the UK. Net cost is what the contribution costs you from take-home after all relief.
The National Insurance saving is four times larger for someone on £40,000 than for someone on £90,000, because the higher earner is only saving the 2% rate on income already above the upper earnings limit. The higher earner still comes out with a lower net cost overall — that is the income tax relief doing the work — but the specifically-salary-sacrifice part of the benefit is a middle-earner phenomenon. It is the opposite of how the arrangement is usually pitched.
There is a second gain that rarely gets a mention: student loan repayments are calculated on your reduced salary too. If you are repaying a loan, sacrifice cuts 9% of the sacrificed amount off your repayments as well. Whether that is a good thing depends on your view of clearing the loan, but it is real money in your pocket each month.
And your employer saves their own National Insurance on the sacrificed amount. Some employers pass part or all of that saving into your pension. Many do not, and never mention it. It is worth asking, because the answer is sometimes yes for the asking.
What you give up
Everything here follows from one fact: your gross salary is genuinely lower. Not notionally, not for tax purposes only — lower.
- Mortgage borrowing. Lenders work from gross salary. A £5,000 sacrifice can reduce what you can borrow by a multiple of that, which is the single most common reason people pause or unwind an arrangement. Some lenders will add the sacrifice back if you explain it; plenty will not, and you will not know which until you apply.
- Statutory maternity, paternity and shared parental pay. These are based on average earnings over a set reference period. Sacrificing during that window reduces the pay you receive, and for statutory maternity pay the first six weeks are earnings-related, so the effect is not trivial. If you are planning a family, the timing of this matters more than the amount.
- Death-in-service and income protection cover. Frequently set as a multiple of salary. A lower salary can mean lower cover, though many employers base it on pre-sacrifice “notional” or “reference” salary specifically to avoid this. Worth checking which yours uses.
- Redundancy pay. Statutory redundancy is calculated on weekly pay, so a reduced salary can reduce it.
- Anything else keyed to salary — overtime rates, bonus calculations, pay rises expressed as a percentage. Usually these are based on reference salary, but “usually” is not “always”.
None of these are hidden or unfair. They are the logical consequence of earning less on paper, and the money you are not receiving is going into your pension instead. But they are the reason salary sacrifice is a decision rather than an obvious yes.
The floor you cannot go below
Salary sacrifice cannot take your cash pay below the National Minimum Wage. This is a legal limit, not a guideline, and employers are required to cap arrangements to prevent it. For lower-paid workers it can rule the option out entirely, or restrict how much can be sacrificed — which is a slightly bleak irony given the table above shows the National Insurance saving is proportionally most valuable to people further down the scale.
The change coming in April 2029
This is the part not yet reflected in most articles about salary sacrifice, and anyone weighing it up over a multi-year horizon should know about it.
From April 2029, only the first £2,000 a year of employee pension contributions made through salary sacrifice will remain free of National Insurance. Contributions above that will attract both employee and employer National Insurance, in the same way ordinary workplace pension contributions do.
Some important qualifications. Income tax relief is not changing — pension contributions remain relieved from income tax, subject to the usual limits, above and below the cap. You can still sacrifice more than £2,000; the excess simply stops being NI-free. And employer contributions remain outside National Insurance entirely, which is a meaningful distinction for anyone whose employer contributes generously.
On the government’s own assessment, most employees making typical contributions will not be affected, because most people sacrifice less than £2,000 a year. But if you sacrifice heavily — and people using sacrifice to manage down towards the £100,000 threshold often do — the arithmetic changes from 2029. Illustratively, someone sacrificing £10,000 has £8,000 over the cap, which at the 8% employee rate is £640 of National Insurance a year that is not currently payable.
April 2029 is a long way off and announced tax changes have been known to move. It is not a reason to do anything today, but it is a reason not to treat the current position as permanent.
Where sacrifice earns its keep
Two situations where it does something the other arrangements cannot:
- Middle earners below the upper earnings limit, who save the full 8% rather than 2%. This is the sweet spot, and it is not where the arrangement is usually marketed.
- Anyone near an income threshold. Because sacrifice reduces gross pay, it reduces adjusted net income — which is the test used for the personal allowance taper above £100,000, for Tax-Free Childcare, for the free childcare hours, and for the High Income Child Benefit Charge. Around £100,000 the combined effect is unusually large, which we cover in the £100,000 tax trap.
Frequently asked questions
Can I change my mind?
Not freely. It is a contract variation, and employers typically only allow changes at set points or on a “lifestyle event” such as a birth, marriage or a partner losing their job. Ask what your employer’s rules are before you start, not after.
Does it affect my State Pension?
It can, in principle, if sacrifice takes your earnings below the level at which you build up a qualifying year. For most people earning comfortably above that it makes no difference, but it is a real consideration for part-time and lower-paid workers.
Is it the same as “salary exchange”?
Yes. Employers use both terms, along with “SMART” pensions. Same mechanism.
My employer offers it. Should I take it?
That depends entirely on things this page cannot see — whether you are about to apply for a mortgage, whether you are planning a family, how your death-in-service cover is calculated, and how much you earn. The trade-offs above are the questions to ask; a regulated financial adviser can help you weigh them.
Does it work for things other than pensions?
Yes — cycle-to-work and ultra-low-emission car schemes are common. The April 2029 change described here applies to pension contributions specifically.
I’m in Scotland. Does it work the same way?
The National Insurance side is identical, because NI is not devolved. The income tax saving follows the Scottish rates, which have more bands — see pension tax relief in Scotland.
Where to go from here
- Pension tax relief calculator — compare sacrifice against the other two arrangements on your salary
- Relief at source vs net pay — which one you are on now
- The £100,000 tax trap — where reducing adjusted net income is worth the most
- Salary calculator — what any of this does to your monthly take-home
This is general information about how salary sacrifice works, not financial advice and not a recommendation to enter or leave such an arrangement. Rates and thresholds are for the 2026/27 tax year; the April 2029 change described here is a government announcement and announced measures can change before they take effect. Figures cover income tax and employee National Insurance only and assume a standard tax code with no other income. For advice tailored to your circumstances, speak to a regulated financial adviser; for free and impartial guidance, MoneyHelper is a good place to start. HMRC’s guidance is on GOV.UK.
Last updated: July 2026