Buy-to-Let Mortgage Guide UK 2026

What is a buy-to-let mortgage?

A buy-to-let (BTL) mortgage is a loan designed for purchasing a property you intend to rent out rather than live in. They work differently from residential mortgages in several important ways — from how affordability is assessed to the deposit required and the tax treatment of costs.

Key differences from a residential mortgage

• Higher deposit: Typically 25% minimum (vs 5–10% for residential)
• Rental income assessment: Lenders assess affordability based on expected rental income, not just your salary
• Higher rates: BTL mortgage rates are typically 0.5–1.5% higher than equivalent residential deals
• Interest-only options: Widely available for BTL — many landlords use interest-only to maximise monthly cashflow
• No government schemes: Help to Buy, Shared Ownership etc. don't apply to investment properties

How much deposit do I need?

Most BTL lenders require a minimum 25% deposit, meaning you borrow up to 75% LTV. Some lenders will go to 80% LTV (20% deposit) but rates are significantly higher. Having a larger deposit — 35–40% — unlocks the best rates and strongest rental yield calculations.

How is affordability assessed?

BTL lenders use a rental coverage ratio rather than income multiples. The most common calculation requires the monthly rent to cover 125–145% of the mortgage interest payment at a stressed rate (typically 5–6%, regardless of the actual deal rate).

Example: If your mortgage interest payment is £800/month, the lender needs rental income of £1,000–£1,160/month to approve the loan. A mortgage adviser will calculate this precisely for your target property.

What types of BTL mortgage are available?

Standard buy-to-let

For individuals purchasing a standard residential property to let to private tenants. The most straightforward option.

HMO mortgage (House in Multiple Occupation)

For properties let to 3+ unrelated tenants sharing facilities. Requires a specialist lender and an HMO licence.

Limited company BTL

Many landlords now purchase through a limited company (SPV) for tax efficiency. Mortgage rates are slightly higher, but you can deduct mortgage interest costs fully against rental income — an advantage lost for individual landlords since 2020.

Portfolio landlord mortgage

For landlords with 4+ mortgaged BTL properties. Lenders assess your whole portfolio rather than individual properties.

Tax considerations for buy-to-let

BTL tax has become significantly more complex since 2017. Key points:

• Mortgage interest relief: Individual landlords can no longer deduct mortgage interest from rental income. You get a 20% tax credit instead — which hits higher-rate taxpayers hardest.
• Stamp duty surcharge: 3% surcharge on the purchase price applies to BTL and second homes
• Capital gains tax: Payable on profit when you sell, after your annual CGT allowance
• Income tax: Rental profit is added to your income and taxed at your marginal rate

Is buy-to-let still worth it in 2026?

BTL remains viable for the right investor in the right location, but the margin for error is smaller than a decade ago. Higher mortgage rates, increased stamp duty, and reduced tax relief have squeezed yields. That said, rental demand remains extremely high across the UK and rents have risen significantly since 2022 — partially offsetting the rate impact.

Professional advice is more important than ever. A specialist BTL mortgage adviser can find the most efficient structure and lender for your specific goals.