Every £1,000 You Overpay Your Mortgage Costs You £660 in Lost Tax Relief — Put It in Your Pension Instead

Pension contributions are the closest thing to free money in UK personal finance. A basic-rate taxpayer gets 20% relief — £100 into the pension costs £80 out of pocket. A higher-rate taxpayer at 40% effectively pays £60 for £100 of pension contribution. Additional-rate taxpayers at 45% pay just £55.

Compare that with mortgage overpayment. Every £100 overpaid costs exactly £100. There's no government top-up, no employer match, no tax refund. You save interest — yes — but you save interest on a rate that's been falling for two years and is expected to fall further when the MPC meets on 30 April.

The current annual allowance of £60,000 means most people aren't close to maxing out their pension contributions. If you're earning £55,000, overpaying your mortgage by £500 a month instead of contributing to your pension costs you £200 a month in lost tax relief. That's £2,400 a year the government would have given you, voluntarily surrendered to your mortgage lender. Over a decade, that £24,000 in forfeited relief — invested and compounding — becomes north of £35,000. Our tax planning hub covers the full range of reliefs available to UK taxpayers, but pension relief remains the single largest one most people underuse.

Compound that loss over 25 years and the gap widens dramatically — see <a href="/posts/overpaying-your-45-mortgage-costs-you-52000-in-lost-isa-compounding-run-the/">the full £52,000 compounding cost of overpaying a 4.5% mortgage</a> instead of feeding the ISA.

The Bank of England has cut rates four times since August 2024 — from 5.00% down to 3.75%. Swap rates, which drive fixed mortgage pricing, have been pulling deals below 4.65% this week. When you overpay at 4.65%, your guaranteed return is 4.65%. When the BoE cuts again — markets are pricing at least one more cut before year-end — that return compresses further.

Pension tax relief doesn't compress. It doesn't fluctuate with markets or monetary policy. A 40% taxpayer who puts £1,000 into a pension gets £400 back from HMRC regardless of what Bank Rate does. That's a 66.7% immediate return on the net cost (£600 in, £1,000 invested). No mortgage overpayment can compete with that.

If your employer offers contribution matching, the arithmetic becomes absurd. An employer matching 5% on a £55,000 salary adds £2,750 free. Combined with 40% tax relief, every £1 you contribute effectively becomes £2.75 in your pension. You'd need a 175% guaranteed return from mortgage overpayment to match that — which last happened roughly never.

Consider the trajectory. In August 2024, Bank Rate stood at 5.00%. Today it's 3.75%. If another cut follows the April 30 MPC meeting, Bank Rate could reach 3.50% by summer. A two-year fix taken out at 4.65% today will look expensive by remortgage time — and the "guaranteed return" of overpaying that fix will have been 4.65% while your pension was earning 40% relief plus market growth plus employer matching. The window where mortgage overpayment beats pension contributions has been closing since August 2023, and it isn't coming back until inflation forces rates upward again.

Mortgage overpayment saves you money — but it saves you the same money whether you overpay in year 1 or year 15. The interest saving is linear: £500 overpaid saves roughly £23 in monthly interest on a 4.65% mortgage.

Pension contributions compound. A £500 monthly contribution with 40% tax relief (so £833 actually invested) earning 5% real returns grows to roughly £308,000 over 20 years. The mortgage overpayment on a £200,000 balance at 4.65% saves approximately £28,000 in total interest and clears the debt 7 years early.

The 20-year difference: £280,000 in favour of the pension. Even if investment returns are mediocre — say 3% real — the pension pot still reaches £223,000. You'd need negative real returns over two decades for mortgage overpayment to win on pure value.

This doesn't account for the tax-free lump sum. At retirement, you can withdraw 25% of your pension tax-free — currently up to £268,275 under the lump sum allowance. On a £308,000 pot, that's £77,000 in cash, tax-free. You could use it to clear any remaining mortgage balance and still have tens of thousands left. For a full breakdown of how pension drawdown compares to other options, see our pension strategies guide.

Here's the detail that makes mortgage overpayment look negligent. If your employer matches pension contributions — even partially — and you're diverting that money to your mortgage instead, you're declining free salary.

The 2026/27 workplace pension minimum is 8% of qualifying earnings (5% employee, 3% employer). Many employers match above this. Some match pound for pound up to 10%. If your employer matches 5% and you earn £55,000, diverting £500 a month to your mortgage instead of your pension forfeits £229 a month in employer contributions. Over 20 years, that's £54,960 in employer money you never received.

Add tax relief and employer matching together, and the pension contribution is earning you an immediate return of over 100% before the money is even invested. Your mortgage lender charges you 4.65%. The opportunity cost of overpayment is staggering.

The most common objection: "My employer only matches the minimum 3%." Even at 3%, the arithmetic still favours the pension. On £55,000, that's £1,650 in annual free contributions. Add 40% tax relief on your own £500 monthly, and you're getting £200 a month in relief plus £137.50 a month in employer matching — £337.50 a month in free money that mortgage overpayment simply does not generate. At any level of employer matching above zero, the pension dominates for higher-rate taxpayers. The only scenario where mortgage overpayment wins outright is when there's no employer matching, you're a basic-rate taxpayer, and your mortgage rate exceeds 6%. That combination hasn't existed since early 2024.

The mortgage overpayment crowd will say: "But a pension is invested, so I could lose money." This is technically true and practically misleading.

A diversified global equity fund — the default option in most workplace pensions — has never delivered negative returns over any 20-year period in history. Not during 2008. Not during the dotcom crash. Not during COVID. The question isn't whether you'll make money over 20 years; it's how much.

The real risk is the pension access restriction. You can't touch pension money until age 57 (rising from 55 for most people from 2028). If you need liquidity before then, overpaying the mortgage does make cash available through remortgaging. But for money you won't need for decades, locking it away in a tax-advantaged pension wrapper is a feature, not a flaw — it prevents you from spending it.

For a comprehensive view of pension options and strategies, the key question isn't whether pensions are risky. It's whether forgoing 40% tax relief to save 4.65% interest counts as sound financial management. It doesn't.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions.