Updated July 2026 · Rates unchanged since April 2023
A buy-to-let limited company pays corporation tax on its rental profit. The rates for 2026 are the same ones introduced in April 2023: 19% on taxable profits up to £50,000 (the small profits rate) and 25% above £250,000 (the main rate), with marginal relief smoothing the transition in between. Most single-property and small-portfolio companies pay 19% on everything.
Between £50,000 and £250,000 you don't pay a blended rate — you pay 25% on the whole profit and then subtract marginal relief of 3/200 × (£250,000 − profit) (for a standalone company with a 12-month period and no dividends received). A company with £60,000 of taxable profit pays £15,000 at 25%, minus relief of 3/200 × £190,000 = £2,850, leaving £12,150 — an effective rate of about 20.3%. The catch worth knowing: each extra pound of profit inside the band is effectively taxed at 26.5%, which matters when you're deciding whether to bring forward a repair.
The £50,000 and £250,000 limits are divided by one plus the number of your associated companies — broadly, other companies under the same control. If you and your spouse control two SPVs, each company's small-profits limit drops to £25,000. This is one of the most commonly missed boxes on the CT600, and one of the questions our wizard asks explicitly. The limits are also pro-rated for periods shorter than 12 months.
Personal landlords lost full interest relief under Section 24 — they get only a 20% basic-rate credit. A company deducts its mortgage interest in full before tax, because for a company the interest is a loan-relationship debit set against the property business profit. On the return it shows up as a "non-trading loan relationship deficit" — our engine handles that wording and the right CT600 boxes for you. Only the interest is deductible: the capital part of your mortgage payment never is, for anyone.
A company lets one house for £18,000 a year, with £3,800 of allowable expenses (agent fees, repairs, insurance) and £6,200 of mortgage interest:
| Rent received | £18,000 |
| Allowable expenses | (£3,800) |
| Property business profit | £14,200 |
| Mortgage interest (deducted in full) | (£6,200) |
| Taxable profit | £8,000 |
| Corporation tax at 19% | £1,520 |
Dividends the company pays you are not deductible — they come out of profit after tax, and you may pay personal dividend tax on them separately.
Corporation tax is payable 9 months and 1 day after the accounting period ends; the return (CT600, computation and accounts, all in iXBRL) is due 12 months after. Since HMRC's free filing service closed in March 2026, the return must be filed through commercial software — here's what filing actually involves.
The buy-to-let company tax calculator applies these exact rules — including marginal relief, associated companies and financial-year straddling — using the same engine that prepares our returns.
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