Salary Sacrifice £40,000 of Bonus and HMRC Hands You £22,800 Back — The Best Deal in British Finance

Start with the cash option. A bonus of £40,000 to someone already earning above £50,270 is taxed at 40% income tax and 2% employee NI — a 42% combined rate. You keep £23,200. Put £20,000 into an ISA and the last £3,200 sits in a general investment account, already taxed.

Now the sacrifice option. The £40,000 never hits payroll as earnings, so there's no income tax and no employee NI. It lands in the pension intact. Your employer also saves the 15% Class 1 secondary NI contribution on that £40,000 — £6,000. Most decent UK employers route this back into your pension as an 'employer NI uplift', taking the total contribution to £46,000. Some only share half, some share nothing. MoneyHelper's salary sacrifice explainer walks through the mechanics.

The delta isn't a close-run comparison.

Before any investment return, you're ahead by £16,800 if your employer keeps the NI rebate, and £22,800 if they pass it back.

Assume a 50-year-old who won't touch the money until 57 — the minimum pension access age rises to 57 in April 2028, so that's seven years. Assume 5% real returns after fees. A 40-year-old with 17 years is a cleaner comparison.

Over 17 years at 5%:

• £23,200 in an ISA grows to £53,200
• £40,000 in a pension grows to £91,700
• £46,000 (with employer NI rebate) grows to £105,500

The ISA comes out tax-free. The pension gets the 25% tax-free lump sum (capped at £268,275 under current rules), with the rest taxed at your marginal rate in retirement. If you're a basic-rate taxpayer at 67 — which most high earners eventually become once salary stops — the tax take on the £91,700 is roughly 15%, netting around £78,000. The full-rebate version nets about £90,000.

Against an ISA's £53,200, that's £25,000–£37,000 more spendable money, for the same gross bonus. And that's assuming the employer pockets the NI rebate — which you can negotiate.

There's a subset of earners for whom salary sacrifice is effectively mandatory: anyone whose bonus pushes them between £100,000 and £125,140. The personal allowance tapers by £1 for every £2 above £100,000, creating a marginal rate of 60% (plus NI, plus loss of tax-free childcare and 30 free hours if you have young children). HMRC's Income Tax rates and allowances spells out the bands.

Sacrifice bonus back below £100,000 and you dodge the personal-allowance taper, keep tax-free childcare, and keep the government's 30 free childcare hours. A parent with two children under five can save £10,000+ a year in childcare costs alone, on top of the 60% marginal tax saving. Combined effective relief can exceed 70%.

I cannot think of another single financial decision in the UK tax code that reliably delivers a 70% government top-up. Not LISAs (25%, capped at £1,000/year). Not pension carry-forward in itself. Not VCTs (30%, high-risk, 5-year lock). The 60% tax trap between £100k and £125,140 is a uniquely punishing quirk — and salary sacrifice is the cleanest way around it.

The standard pension annual allowance is £60,000 for 2026/27. Sacrifice more than that in a year and the excess is taxable at your marginal rate — the allowance charge wipes out the relief. Two things to know:

1. Carry-forward. Unused allowance from the previous three tax years rolls forward, provided you were a member of a registered pension scheme in those years. Someone who's only contributed the employer auto-enrolment minimum for three years could have £180,000+ of carry-forward room. See our pension tax relief guide for the rules.

2. Tapered allowance. If adjusted income exceeds £260,000, the annual allowance tapers down by £1 for every £2 over, to a £10,000 floor. Very high earners have less room — but they also have the most to gain from sacrificing what they can, because their marginal rate is still 45%.

For the typical £60k–£120k earner getting a £40,000 bonus, the annual allowance is not a binding constraint. Sacrifice the lot.

The standard objection: 'Pension rules change every Budget — why lock money away under rules that might be worse in 20 years?' It's a real risk. But three things temper it.

First, pension changes are almost always grandfathered. The lifetime allowance was abolished in April 2024, not retroactively cut. The 25% tax-free lump sum was capped, not removed. The tapered allowance tightened in 2020 but existing accrued funds were untouched. Governments face political backlash if they retrospectively tax pensions — it's one of the few Treasury moves that reliably costs elections.

Second, even a 10% haircut on tax-free cash or marginal-rate drawdown still leaves salary sacrifice ahead of a cash ISA route for anyone whose retirement marginal rate will be lower than their working marginal rate. The 42% tax saved today is a much larger discount than the 5–10% drag a worst-case reform would impose.

Third — and this is the kicker — the alternative isn't rule-stable either. The ISA annual allowance has been cut for certain products and the Cash ISA allowance is proposed to drop to £12,000 from April 2027. Any future Labour or Conservative government will tweak both. Refusing to sacrifice on rule-change grounds and then putting the money in an ISA is not a hedge — it's just missing the 42% today in exchange for the same long-run political risk.

For the opposite view, our sister piece makes the case for taking the cash and filling the ISA in full.

Three exceptions where the maths flips:

• You'll need the cash inside five years. A house deposit, a business investment, a known future expense. Pensions are illiquid. Sacrificing then scrambling to borrow at 5–6% rates to cover a cash shortfall burns the advantage. Short-horizon money belongs in a top-paying cash ISA at 4.6%+, not locked up until 57.
• Your earnings are near the NI primary threshold (£12,570). Sacrifice below that and you lose state pension qualifying years and risk Statutory Maternity Pay or mortgage affordability. Employers should warn you — most don't.
• Your employer doesn't offer salary sacrifice. Some smaller firms don't have the payroll setup. Net-pay and relief-at-source workplace schemes still give higher-rate relief via the tax return, but you lose the NI saving. Worth a direct conversation with HR.

Beyond these, if you're a higher-rate earner with a bonus, the cost of not sacrificing is 42p of every pound. That's not a hedge — that's a tax on indecision.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions. Past performance is not a reliable indicator of future results. Tax treatment depends on individual circumstances and may change in future.