Spare money each month, and two good homes for it. Here's the arithmetic most people skip before they choose — and the one thing that decides it outright for a lot of business owners.
Anyone who tells you flatly to do one or the other hasn't seen your numbers. What decides it is four things: whether there's employer or company money on the table you're not claiming, whether your tax rate now is higher than the one you'll pay in retirement, how your mortgage rate compares with a cautious growth assumption, and how much a guaranteed, debt-free date is worth to you beyond the arithmetic.
Get those four straight and the answer is usually clear enough. Skip them and you're guessing — which is what most people do, because the comparison everyone reaches for first is the wrong one.
The instinct is to line up the mortgage rate against an assumed investment growth rate and back whichever number is bigger. Mortgage at 5%, growth assumed at 3% real — mortgage wins, done. It feels like arithmetic. It's missing two-thirds of the sum.
A pension contribution doesn't start at zero and then grow. It starts with an immediate, guaranteed uplift from tax relief before a single pound is invested — 25% for a basic-rate taxpayer, more for higher and additional rate. No mortgage overpayment offers a day-one discount like that.
The relief isn't free money kept forever. Up to 25% of the pot can come out tax-free, and the rest is taxed as income when it's drawn. A fair comparison has to look at what survives after both, not just what goes in.
Pension money is locked until you reach normal minimum pension age — 55 now, rising to 57 in April 2028. People treat that as the mortgage's advantage. It isn't automatically one: money paid into the house is also locked, in the form of equity you can't spend without selling or borrowing against it.
Overpaying the mortgage buys a return exactly equal to the rate, guaranteed, because every pound wipes out interest that would otherwise have been charged. A pension's growth isn't guaranteed at all. The tax relief is the only guaranteed part of the pension side — which is precisely why it belongs in the sum.
Priya is 53, runs a small design studio, and has £500 a month she could put either way. £180,000 left on her mortgage, 5.1%, twelve years to run, monthly payment around £1,675. She's a higher-rate taxpayer once salary and dividends from the business are added together.
An extra £500 a month clears it in 103 months instead of 145 — three and a half years early — and saves roughly £18,700 in interest. Guaranteed, because it isn't exposed to markets at all.
As a higher-rate taxpayer, £500 net automatically becomes £625 gross in the pension, and she can reclaim a further £125 a month through her tax return. Her real out-of-pocket cost falls to £375 a month for £625 landing in the pot.
At 3% real growth — this site's standard working assumption, printed on every plan — that £625 a month builds to roughly £73,000 before tax, for a true cash cost over the period of about £38,600.
Take 25% tax-free and pay basic-rate tax on the rest and Priya keeps roughly £62,000 of that £73,000. Against a total outlay nearly £13,000 lower than the mortgage route's £51,500, and against a guaranteed £18,700 saved the other way.
For a higher-rate taxpayer with no employer match at stake, the tax relief on the way in is doing more work than a 5.1% mortgage rate can undo — even allowing for tax on the way out and a growth rate that isn't guaranteed. That's arithmetic, not a recommendation, and it's also why the answer moves so much once you drop from higher-rate to basic-rate: the relief that made the pension route win is the first thing to shrink.
Before any of the above: is there money on the table you're not claiming? If an employer matches contributions up to a certain percentage and you're paying in less than that, the match is a guaranteed return no mortgage rate will ever touch. Claim all of it before either side of this comparison starts.
For an owner-director it works differently again. A contribution the company makes directly into a pension is deductible against the company's own corporation tax and isn't liable to National Insurance either side, whereas the same money extracted as a dividend first is taxed as a dividend on the way out before it ever reaches a personal bank account or a mortgage overpayment. That difference is real and it's usually sizeable — but the exact figures depend on the company's profit level and its existing salary and dividend split, which is a conversation for your accountant rather than something to estimate here.
An unclaimed employer or company match. A meaningfully higher tax rate now than you expect in retirement. Headroom left in this year's £60,000 annual allowance that would otherwise go unused. Plenty of years left before you'd want to touch either pot.
A rate that's unusually high against a cautious growth assumption. A strong preference for being guaranteed debt-free by a specific date, especially one close to when you plan to stop working. Already using most of this year's pension allowance. A basic-rate tax position now with no clear sign that it'll be lower later.
No emergency cash at all. Locking money into either a pension or a mortgage before you have a few months of spending sitting somewhere accessible is usually the mistake underneath the mistake — it's what forces expensive borrowing when something breaks.
Most people don't actually have to choose one exclusively. Splitting £500 as £300 mortgage and £200 pension, or the other way round, is a perfectly reasonable answer if the arithmetic comes out close, and closeness is itself useful information.
Two facts turn this from a guess into arithmetic: your actual marginal tax rate today, and whether an employer or company match is sitting unclaimed. Get those, then run the comparison on your own mortgage balance and rate rather than Priya's.
The free projection shows what either route does to the age your money runs out, on your own figures. If tax-free cash is part of how you'd eventually clear the mortgage rather than paying it down now, the tax-free cash guide covers that version of the same question. And if several of these are moving against each other at once — the mortgage, the pension, a business, a stop date you haven't fixed — that's what the Financial Plan is built to untangle, with UK tax applied properly year by year rather than estimated on a page like this one.
Yes, in one specific case: an unclaimed employer or company pension match. If your employer will add money on top of what you contribute and you're paying in less than the threshold that triggers it, claim the match first, before comparing anything else. It's a guaranteed uplift that no mortgage rate can compete with, and leaving it unclaimed to overpay a mortgage instead is close to the only genuinely wrong move available in this whole comparison. Once the match is fully claimed, the answer stops being clear-cut and starts depending on your tax rate, your mortgage rate, how much allowance headroom you have left this year, and how you weigh a guaranteed outcome against one that isn't.
The relief is smaller, so the comparison is closer, and for some people it tips the other way entirely. A basic-rate contribution still gets a 25% uplift from relief, which is genuinely good, but it's roughly half the day-one boost a higher-rate taxpayer gets, and there's no self-assessment reclaim adding to it. Run Priya's worked example again at basic rate rather than higher rate and the pension route's £73,000 pot costs closer to £500 a month in real terms rather than £375, which narrows the gap against the mortgage's guaranteed £18,700 considerably. If you expect to stay basic-rate in retirement too, the tax-in versus tax-out advantage shrinks further still, which is exactly why this isn't a rule that applies to everyone equally.
It usually strengthens the case for the pension, sometimes considerably, because a contribution the company pays in directly avoids both the dividend tax and the National Insurance that extracting the same money as salary or dividends first would trigger. How much that's worth depends on your company's profit level, its corporation tax position, and how you currently split salary and dividends, none of which can be estimated generically on a guide like this one. What this page can do is show you what either route does to your own lifetime projection. Working out the most efficient way for your specific company to get money into a pension is properly your accountant's job, not ours.
Yes, and for a lot of people that's the sensible answer rather than a compromise. Splitting £500 a month as £300 towards the pension and £200 towards overpaying the mortgage, or any other split, is entirely reasonable, particularly if the arithmetic on your own numbers comes out close between the two routes. The one thing worth checking before splitting anything is whether an employer or company match is fully claimed first, because that part of the decision genuinely isn't close. After that, splitting is less about optimising to the last pound and more about not having to bet everything on one growth assumption or one interest rate holding still for a decade.
Only up to your available allowance, and only if the tax relief still makes sense doing it that fast. The standard annual allowance is £60,000, and you may have unused allowance carried forward from the previous three tax years if you didn't use it at the time. Beyond that limit, extra contributions stop attracting relief and become considerably less attractive, at which point overpaying the mortgage or saving outside a pension usually makes more sense for anything above it. For most people the constraint isn't the allowance, it's simply how much is genuinely spare each month once spending, and any debts more expensive than the mortgage, are accounted for.
Start with two facts rather than a feeling: your real marginal tax rate today, from a payslip or your last tax return, and your mortgage's actual rate and remaining term, from your last annual statement. Then check whether an employer or company match is sitting unclaimed, because that changes the entire calculation before anything else is considered. With those three things you can run the same comparison shown above on your own numbers rather than Priya's, and the free projection will show what either route does to the age your money runs out. If the picture has several parts pulling against each other at once, that's what the Financial Plan is for.
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