ISA vs buy-to-let with £50k: the honest comparison

2026-07-16 money, property, investing, tax

Same £50,000, same ten years, same higher-rate taxpayer. One goes into a stocks & shares ISA, one becomes a buy-to-let deposit. The 2026/27 tax rules pick a clear winner.

Rates verified against gov.uk — 2026/27 tax year (as of 21 June 2026)

You've got £50,000. Every family barbecue has one relative certain you should buy a rental ("bricks and mortar, can't go wrong") and one convinced the stock market does it better without the 2am boiler calls. Both are arguing from vibes. Let's argue from arithmetic instead: same £50,000, same ten years, same higher-rate taxpayer, 2026/27 tax rules applied properly to each side. These are the default assumptions in our investment comparison calculator, so you can rerun everything with your own numbers the moment you disagree with mine.

Corner one: the stocks & shares ISA

£50,000 into a global index fund inside an ISA, growing at 7% a year. One honest wrinkle before we start: the ISA allowance is £20,000 per tax year, so sheltering £50,000 actually takes you until year three (£20k, £20k, £10k). Do it and the sums are almost embarrassingly simple.

ISA after 10 years

Final value: £100,483
Profit: £50,483 · Tax on it: £0
Effective return: 7.2% a year, compounded, nothing to do

Skip the ISA wrapper and hold the same fund in a general account and the picture sours: dividend tax along the way at 35.75%, then capital gains tax at 24% on nearly all of the gain (the CGT allowance is a token £3,000 now). Result: £85,804 — the wrapper alone is worth about £14,700 over the decade. Wrap first, argue later.

Corner two: the buy-to-let

Property's pitch is leverage. Your £50,000 becomes a 25% deposit on a £200,000 house, so 3% growth works on £200,000 rather than £50,000. Fine — but leverage is bought with costs the barbecue never mentions, and they start before the first tenant moves in.

The same £50k as a BTL deposit, 2026/27

£200,000 purchase → SDLT with the 5% surcharge: £11,500, plus ~£2,500 fees
True cash in: £64,000, not £50,000
Rent at a 6% gross yield: £12,000 · running costs (25%): £3,000 · mortgage interest at 5.5% on £150,000: £8,250
Tax under Section 24: £1,950 → cash flow in year one: −£1,200

Read that last line again. At today's average yield and mortgage rate, a higher-rate taxpayer's ordinary leveraged BTL loses money every month. Section 24 taxes you on rent-minus-costs while ignoring most of your mortgage interest, so you pay £1,950 of tax on a property that put −£1,200 in your pocket. Ten years of that is £12,000 of drip-fed losses you're covering from your salary.

The exit is where property claws some back. At 3% growth the house sells for £268,783; pay off the mortgage, hand HMRC £15,788 of CGT (24%), and you're left with a final position of £90,995 from £64,000 in. Profit: £26,995. That's 3.6% a year. The unleveraged, untaxed, unmanaged ISA made nearly double the return and £23,500 more money — while you were repricing insurance and chasing a plumber in the rain.

Where property wins the rematch

Now, before the landlords in the room close the tab: change two assumptions and the fight flips, and it's worth being precise about which two.

Growth. At 5% capital growth instead of 3%, the same deal ends at £134,312 — a 7.7% annual return that beats the ISA. Leverage cuts both ways, and on the upside it cuts hard. The question is whether you're comfortable betting five figures of stamp duty on your growth forecast.
Yield. At an 8% gross yield (realistic in parts of the North, or with an HMO) the cash flow turns positive — about £600 a year — and the ten-year return rises to 5.5%. Better, still short of the ISA at these growth rates.
The purchase itself. The comparison above buys at full market price. Buy 10–15% below value, or force appreciation with a refurb, and you've imported return the market didn't give you. That's the honest version of "property beats shares": it beats them when you do work the index fund doesn't ask of you.

And one asymmetry the spreadsheet can't capture: the ISA result needs no skill and roughly four hours a year. The winning property result needs sourcing, refurb management, tenants and a decade of compliance. If that work appeals to you, property is a business you can genuinely be paid well for running. If it doesn't, you now know exactly what the barbecue advice costs.

FAQs

Is 7% a fair assumption for the ISA?

It's in line with long-run global equity returns before inflation, and it's an assumption, not a promise — a bad decade happens. The fair comparison is that 3% property growth is an assumption too, and the leveraged side is far more sensitive to being wrong: at 1% growth the BTL's ten-year return drops below cash savings. Test both ends in the calculator before you believe either camp.

Doesn't the £20,000 ISA limit ruin the comparison?

Barely. While the unsheltered £30,000 waits its turn (year two and three), it faces dividend tax on roughly 2% yields and little else — a few hundred pounds against £14,700 of tax the fully-unwrapped account pays over the decade. The bigger practical point: if you already use your allowance every year, the £50,000 can't all be sheltered on top, and the general-account figure of £85,804 becomes the honest benchmark.

What if mortgage rates drop?

Each 1% off the rate saves £1,500 a year on the £150,000 mortgage — £125 a month — which turns our −£1,200 cash flow positive. Rates are the swing variable for the income side of BTL, just as growth is for the exit. Neither is in your control, which is worth remembering when either camp talks in certainties.

Shouldn't I just use a pension instead?

If the money is genuinely for later life, higher-rate relief on the way into a pension is hard to beat with either option here. The trade is access: the ISA is available any time, the pension isn't until 55 (rising to 57 from 2028). Different question, different article.

The takeaway

On average assumptions — average yield, average growth, market-price purchase — the ISA wins, and it isn't close: 7.2% against 3.6%, with zero tax and zero tenants. Property only overturns that verdict when you bring something extra to it: above-average yield, below-market buying, forced appreciation, or a bolder growth assumption than we'd put in print. Plenty of investors do bring those things; that's a business plan, though, not a default. With £50,000 and no appetite for the work, fill the ISA.

Guidance only. BrickCrunch provides general information, not financial, tax or legal advice. Our calculators give estimates only, using rates we verify against gov.uk — always confirm figures and your own position before acting.