Investing in residential property requires understanding mortgage financing and taxation in the UK. A buy-to-let mortgage is designed specifically for properties purchased to let to tenants. Unlike residential loans, lenders assess borrowing primarily on rental income rather than personal earnings alone.
The landscape for landlords has changed significantly. Between stricter stress-testing guidelines, the limitation of mortgage interest tax relief, and stamp duty surcharges, investors must evaluate each purchase with care. This guide explains deposit thresholds, rental coverage ratios, Section 24 tax restrictions, and stamp duty rules for 2026/27.
Deposit requirements for buy-to-let mortgages
Lenders view rental properties as carrying greater risk than owner-occupied homes because landlords face void periods, tenant arrears, and repairs. Consequently, deposit minimums are higher:
- Typical deposit (25%): Most mainstream lenders require a minimum deposit of 25%, representing a maximum loan-to-value ratio of 75%.
- Minimum deposit (20%): A limited selection of specialist lenders permits a 20% deposit (80% loan-to-value), though rates and fees are higher.
- Lower-rate tier (40%): To secure the most competitive interest rates, landlords generally need a 40% deposit (60% loan-to-value).
The table below outlines deposit capital across typical purchase prices:
| Property Price | 20% Deposit (80% Loan) | 25% Deposit (75% Loan) | 40% Deposit (60% Loan) |
|---|---|---|---|
| £200,000 | £40,000 | £50,000 | £80,000 |
| £250,000 | £50,000 | £62,500 | £100,000 |
| £300,000 | £60,000 | £75,000 | £120,000 |
| £400,000 | £80,000 | £100,000 | £160,000 |
Most buy-to-let mortgages are arranged on an interest-only basis, minimising monthly outlays while retaining rental income for maintenance and reserves.
Rental coverage ratio and stress testing
Lenders evaluate affordability through the Interest Cover Ratio, measuring expected rental income against mortgage interest. Lenders test the loan against a hypothetical stress rate, commonly 5.5% or 2% above the actual pay rate:
- Basic-rate taxpayers and limited companies: Lenders apply a minimum rental coverage ratio of 125%.
- Higher-rate and additional-rate taxpayers: Lenders require a coverage ratio of 145% to account for personal tax liabilities.
To see how this operates, consider an investor purchasing a £240,000 property with a 75% mortgage (£180,000 loan) tested at a 5.5% stress rate:
- The annual stressed interest charge equals £9,900 (£180,000 multiplied by 5.5%), or £825 per month.
- For a basic-rate taxpayer or limited company at 125% coverage, the required monthly rent is £1,031.25 (£825 multiplied by 1.25).
- For a higher-rate taxpayer at 145% coverage, the required monthly rent rises to £1,196.25 (£825 multiplied by 1.45).
If local rents cannot meet this threshold, the buyer must contribute a larger deposit. You can evaluate borrowing capacity and monthly cash flows using the buy-to-let mortgage calculator.
Section 24 tax relief restrictions
Section 24 of the Finance (No. 2) Act 2015 transformed property taxation for individuals. Landlords cannot deduct mortgage interest from gross rental income before calculating taxable profit.
Instead, individual landlords pay tax on rental profit before finance deductions and receive a basic-rate tax credit equal to 20% of financing costs.
This reform disproportionately affects higher-rate taxpayers:
- Under previous rules, a higher-rate taxpayer earning £18,000 in rent with £10,000 in mortgage interest paid 40% tax on net profit of £8,000, incurring a £3,200 bill.
- Under Section 24, the full £18,000 forms taxable income. At 40%, gross tax is £7,200. The landlord receives a 20% credit on the £10,000 finance cost (£2,000), leaving a net tax bill of £5,200.
Because finance costs are not deductible, reported income can push landlords into higher tax brackets. Consequently, many investors now purchase properties through a limited company, where mortgage interest remains deductible as a business expense.
Stamp duty 5% surcharge on additional properties
In England and Northern Ireland, purchasing an additional residential property incurs a 5 percentage point surcharge above standard Stamp Duty Land Tax rates:
| Slice of Property Value | Standard Home Mover Rate | Additional Property Rate |
|---|---|---|
| Up to £125,000 | 0% | 5% |
| £125,001 to £250,000 | 2% | 7% |
| £250,001 to £925,000 | 5% | 10% |
| £925,001 to £1,500,000 | 10% | 15% |
| Over £1,500,000 | 12% | 17% |
On a buy-to-let purchase of £250,000, stamp duty is £15,000, compared to £2,500 for a standard home mover. On a £300,000 purchase, duty reaches £20,000. Landlords must budget for this capital expense in cash at completion.
Frequently asked questions
Can a first-time buyer get a buy-to-let mortgage?
While possible with specialist lenders, most lenders require applicants to own a primary home first. Lenders that accept first-time buyers impose higher income minimums, larger deposits (often 25% to 30%), and stricter stress tests.
Should you buy a buy-to-let property through a limited company?
A limited company allows investors to deduct 100% of mortgage interest against profits and pay Corporation Tax rather than personal income tax. However, company mortgages carry slightly higher interest rates and legal fees. The appropriate structure depends on your personal income band, portfolio scale, and investment horizon.
What happens when a fixed-rate buy-to-let mortgage deal ends?
When a promotional fixed rate ends, the loan transfers to the lender standard variable rate, which is usually significantly higher. Most landlords review remortgage options three to six months before expiration to secure a new fixed deal and prevent steep payment rises.
Information provided for educational purposes, not regulated financial advice. Tax rules and mortgage criteria depend on individual circumstances and may change. Consult a qualified accountant and a mortgage broker authorised by the Financial Conduct Authority before purchasing.