How salary sacrifice works
Salary sacrifice is a contractual arrangement where you agree to give up a portion of your gross salary in exchange for a non-cash benefit — most commonly a higher pension contribution from your employer. Because the sacrificed amount never appears as pay, you don't pay income taxor National Insurance on it. Your employer also doesn't pay the 15% employer NI on that portion of your salary, which some employers choose to pass on to your pension.
A basic-rate taxpayer saves 28% (20% income tax + 8% NI) on every pound sacrificed. A higher-rate taxpayer saves 42% (40% + 2%). So £100 sacrificed from gross pay only reduces your take-home by £72 or £58 respectively — but the full £100 lands in your pension pot. The difference compounds over decades of investing, so even a modest monthly sacrifice can add hundreds of thousands of pounds to a retirement pot.
Salary sacrifice vs relief at source
The alternative is relief at source (RAS), which is the default for many personal and some workplace pensions. With RAS you pay your contribution from net pay, and the provider adds 20% basic-rate tax relief automatically. Higher-rate and additional-rate taxpayers claim the extra relief through self-assessment. Here's how the two compare for a £100/month contribution:
| Salary sacrifice | Relief at source | |
|---|---|---|
| Your gross salary | Reduced by £100 | Unchanged |
| Income tax saved (basic rate) | £20 (automatic) | £25 added by provider |
| NI saved (basic rate) | £8 (automatic) | £0 |
| Into pension pot | £100 | £125 |
| Net cost to you | £72 | £100 |
For the same after-tax cost, salary sacrifice puts more into your pension for basic-rate taxpayers. For higher-rate taxpayers who actually claim their extra relief, the difference closes — but sacrifice still wins on NI.
Does salary sacrifice affect my mortgage application?
Yes. Because salary sacrifice reduces your gross salary on paper, most UK lenders will use your post-sacrifice figure when deciding how much to lend you. If you're sacrificing 8% of a £60,000 salary, lenders may base affordability on £55,200 rather than £60,000 — at typical 4.5x income multiples, that's about £21,500 less borrowing capacity.
Some lenders ask for your pre-sacrifice salary on payslips or will accept a letter from your employer confirming the arrangement. If you're planning to buy a home in the next year, it can be worth pausing or reducing sacrifice before applying — though weigh this against the tax savings you'd be giving up.