Buy-to-Let Tax in 2026: How the Rules Now Hit Small-Portfolio Landlords — and What Making Tax Digital Changes Next

Buy-to-let used to be a fairly simple proposition: buy a property, let it out, declare the profit, pay tax on what was left after costs. That model has been quietly dismantled over the last decade — and the landlords feeling it most are not the large portfolio operators with in-house accountants, but the one-, two- and three-property landlords who treat their letting income as a side activity to be sorted out once a year.

This article walks through how buy-to-let income and gains are actually taxed today, why the rules disproportionately squeeze small-portfolio landlords, and what Making Tax Digital for Income Tax — the biggest change to come — will require from April 2026 onwards.

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How Rental Profit Is Actually Taxed

Rental income is added to a landlord's other income (salary, self-employment, pensions) and taxed at their marginal rate of Income Tax — 20% as a basic-rate taxpayer, 40% as a higher-rate taxpayer, and 45% as an additional-rate taxpayer. There is no separate, lower "landlord rate" — which surprises a lot of people coming into the market for the first time.

Allowable expenses can be deducted before profit is calculated, including:

• Letting agent and management fees
• Repairs and maintenance (not improvements)
• Buildings and contents insurance
• Service charges and ground rent (for leasehold flats)
• Utility bills and council tax paid by the landlord
• Accountancy and legal fees relating to the letting business

What you cannot fully deduct any more — and this is where it gets painful for smaller, more highly-geared landlords — is mortgage interest.

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Section 24: Why Mortgage Interest No Longer Works the Way You Think

Since the rules were fully phased in, landlords can no longer deduct mortgage interest and other finance costs from their rental income before calculating tax. Instead, they receive a flat 20% tax credit on those finance costs, applied after the tax bill has been calculated.

This sounds like a technicality, but it has two serious consequences for smaller landlords:

1. It can push you into a higher tax bracket. Because the full rental income (not the income minus mortgage interest) is what counts towards your tax band, a landlord who looks like a basic-rate taxpayer on paper can be tipped into the higher-rate band — and lose part of their personal allowance if total income passes £100,000.
2. Higher-rate taxpayers lose real money. A higher-rate taxpayer used to get 40% relief on mortgage interest. They now get 20% — meaning the same finance costs are worth half as much in tax relief.

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Capital Gains Tax When You Sell

When a landlord sells a rental property for more than they paid (after deducting costs of purchase, sale and qualifying improvements), the gain is subject to Capital Gains Tax (CGT):

• 18% for gains that fall within the basic-rate Income Tax band
• 24% for gains above that threshold

Every individual has an annual CGT exempt amount, but in recent years this allowance has been cut sharply — leaving far less of any gain untaxed than landlords who bought ten or fifteen years ago might expect. For someone selling a single investment property to fund retirement, downsizing, or release equity, this can mean a significantly larger tax bill than anticipated, often payable within 60 days of completion via a UK Property return — a separate, faster deadline than the normal Self Assessment timetable that catches many smaller landlords off guard.

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Stamp Duty: The Cost of Buying Has Gone Up Too

It isn't only selling and holding that costs more — buying does too. Anyone purchasing an additional residential property (which covers virtually every buy-to-let purchase by someone who already owns a home) pays the standard Stamp Duty Land Tax rates plus a surcharge on top, which now stands at 5% of the purchase price. On a £220,000 property, that surcharge alone adds £11,000 to the up-front cost of getting started — a substantial barrier for someone looking to buy their first or second rental property rather than expand an existing portfolio.

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Furnished Holiday Lettings: A Closed Door

Landlords who ran short-term or holiday lets used to benefit from the Furnished Holiday Lettings (FHL) regime, which gave more generous tax treatment than standard residential lettings — full mortgage interest relief, capital allowances on furnishings, and access to certain CGT reliefs on sale. That regime has now been abolished, and furnished holiday lets are taxed in the same way as any other residential letting. Landlords who built a small portfolio around the short-let model — often exactly the kind of one-or-two-property operator this article is about — have lost a meaningful tax advantage almost overnight.

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Why Small-Portfolio Landlords Feel This More Than Anyone

It's tempting to assume that tax changes hit big portfolio landlords hardest, since they have more properties and more income. In practice, the opposite is often true for several reasons:

• Higher gearing. Landlords with one to three properties are statistically more likely to have bought with a large mortgage relative to the property's value — exactly the position Section 24 penalises hardest.
• No professional support. Larger operators run through limited companies (where the mortgage interest restriction doesn't apply in the same way) and employ accountants. Small landlords are far more likely to be unincorporated individuals filing their own Self Assessment return once a year, with no one flagging the cumulative effect of these changes.
• Tighter margins, less room to absorb shocks. A portfolio landlord can offset a loss-making property against a profitable one. A landlord with a single rental property has nowhere to hide a bad year — a void period, a major repair and a tax bill landing in the same quarter can turn a "side income" property into a loss-making liability.
• Administrative burden lands disproportionately. The records, deadlines and software requirements coming with Making Tax Digital (below) represent a fixed cost in time and money — and a fixed cost is proportionally far heavier on someone with one property than on someone with twenty.

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Making Tax Digital for Income Tax: The Next Big Change

The most significant shift on the horizon is Making Tax Digital for Income Tax (MTD for IT) — a fundamental change in how landlords and sole traders report income to HMRC. Instead of a single annual Self Assessment return, qualifying landlords will need to:

• Keep digital records of income and expenses using MTD-compatible software
• Submit a quarterly update to HMRC summarising income and expenses for that period
• Submit a final declaration at the end of the tax year, replacing the traditional Self Assessment return

This is a genuine change of operating model, not a paperwork tweak. A landlord who currently gathers receipts in a shoebox once a year and hands them to an accountant in January will instead need a system that produces an accurate, exportable summary of income and expenses every quarter, all year round — in a format that compatible software can submit directly to HMRC.

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What This Looks Like in Practice

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How to Stay Ahead of It

1. Know your gross rental income, not just your profit — that's the figure that determines when MTD applies to you.
2. Move off paper and spreadsheets now, not in the month before your MTD start date. Choosing and learning a system under deadline pressure is how mistakes happen.
3. Track every expense as it happens. Quarterly reporting means there's no annual "catch-up" — the discipline has to be continuous.
4. Model your real after-tax position, including the effect of the mortgage interest credit, before assuming a property is profitable on paper.
5. Get ahead of CGT and SDLT costs before you buy or sell — both now represent a much larger share of the total cost of a transaction than they did even five years ago.

PropAI's finances module gives small-portfolio landlords exactly this kind of real-time visibility — tracking income and expenses property-by-property as they happen, producing the kind of organised, exportable records that make MTD-style quarterly reporting straightforward rather than stressful, and giving you a clear, accurate picture of your actual after-tax position rather than a surprise in January.

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