Buy-to-Let Mortgage UK 2026: Complete Comparison Guide

In short: Buy-to-let mortgages are underwritten on rental income, not personal salary. Lenders apply a rental coverage ratio, usually 125% to 145% at a stressed rate. Most products are interest-only. The difference between a good and an average deal over a five-year fix can easily exceed £5,000, which is why using a whole-of-market broker typically pays for itself.

Important: This guide is for general information only. It does not constitute financial advice. Buy-to-let mortgages are not regulated by the Financial Conduct Authority for most investors. Before committing to any mortgage product, speak to a qualified whole-of-market broker who can assess your full circumstances. Your property may be repossessed if you do not keep up repayments on a mortgage.

A buy-to-let mortgage is structurally different from a residential mortgage. The underwriting logic, the affordability tests, and many of the product features work differently. Understanding how lenders assess a BTL application and what drives the rate helps you make better decisions when selecting a product.

How BTL Mortgage Underwriting Works

Residential mortgages are assessed primarily on your income and expenditure. Buy-to-let mortgages are assessed primarily on the property, specifically whether the rental income from that property is sufficient to cover the mortgage payments at a margin.

This is the interest coverage ratio (ICR) test, and it works roughly as follows. The lender takes the proposed monthly interest payment, multiplies it by the required ICR (commonly 125% for basic-rate taxpayers, 145% for higher-rate taxpayers), and requires the monthly rent to meet or exceed that figure. The calculation is done at a stressed rate, typically 5% to 5.5%, not at the actual product rate, to ensure the loan remains affordable if rates rise.

In practice, a property renting at £1,200 per month needs monthly interest payments of no more than £960 at 125% ICR, or £827 at 145%. At a stressed rate of 5.5%, that converts to a maximum loan size of approximately £209,000 at 125% or £180,000 at 145%.

The higher ICR for higher-rate taxpayers reflects Section 24. Because individual higher-rate taxpayers cannot deduct mortgage interest from rental profit (they receive only a 20% tax credit), a greater proportion of their gross rent is consumed by tax, leaving less margin to service the debt. Lenders adjust their stress tests to account for this. If you are unsure how Section 24 affects your rental profit calculation, the landlord tax deductions guide covers the full breakdown.

Personal income is still assessed but plays a secondary role. Most lenders require a minimum personal income of £25,000 to £30,000 as a condition of lending, even if the loan is primarily supported by rental income. Your credit history, existing debt levels, and number of properties you already hold also affect the lender’s decision and the available products.

Loan-to-Value and How It Affects the Rate

The loan-to-value (LTV) ratio is the mortgage amount as a percentage of the property’s value. A £150,000 mortgage on a £200,000 property is 75% LTV.

BTL mortgage rates are tiered by LTV:

• 60% LTV and below: the most competitive rates
• 65% to 70% LTV: competitive, most mainstream lenders active at this tier
• 75% LTV: the maximum for most mainstream BTL lenders
• 80% LTV: available from specialist lenders at higher rates

Moving from 75% to 70% LTV on a £200,000 mortgage means borrowing £10,000 less but can unlock a meaningfully lower rate. On a five-year fix, the rate difference between 75% and 65% LTV has historically been 0.3% to 0.6%. On a £200,000 balance, that is £600 to £1,200 per year or £3,000 to £6,000 over a five-year term.

If you can reduce the LTV by putting in a larger deposit or by allowing equity to build before remortgaging, the rate improvement can be significant.

Fixed, Tracker, and Discount Products

Fixed-rate mortgages set the interest rate for a specified period, typically two, three, or five years. During the fixed term your monthly payment does not change regardless of what happens to the Bank of England base rate. At the end of the fixed term the mortgage reverts to the lender’s standard variable rate (SVR), which is almost always higher. Most borrowers remortgage at or before the reversion to avoid the SVR.

A five-year fix provides longer certainty than a two-year fix but means you are committed to that rate even if market rates fall significantly. If you remortgage early, early repayment charges (ERCs) apply, typically 1% to 5% of the outstanding balance depending on how far through the fixed term you are.

Tracker mortgages follow the Bank of England base rate plus a set margin. If the base rate is 4.5% and the margin is 0.5%, you pay 5%. When the base rate changes, your payment changes. Trackers often have no ERCs (though check this), which means you can remortgage away without penalty if rates rise or a better deal appears. The risk is that payments increase if the base rate rises.

Discount mortgages offer a discount off the lender’s SVR for a specified period. Because the SVR itself can change, these are less predictable than trackers linked to the base rate.

For most landlords who want predictability and are planning for the medium term, a fixed-rate product is the standard choice. The appropriate term depends on where you think rates are heading and how much flexibility you need.

Arrangement Fees and the True Cost

The headline rate shown in a BTL mortgage comparison is not always the true cost of the product. Arrangement fees, also called product fees, booking fees, or completion fees, add to the total cost of borrowing.

A product with a rate of 3.99% and a £2,000 fee can cost more over a two-year term than a product at 4.25% with no fee, depending on the loan size and term.

The simplest comparison is the total cost over the initial fixed or tracker period: (monthly payment x number of months) plus arrangement fee plus any booking fee. Most mortgage comparison tools and brokers can calculate this.

Arrangement fees can usually be added to the loan rather than paid upfront. If you add the fee to the loan, you pay interest on it for the mortgage term, which increases the total cost slightly.

Free legal and free valuation incentives from lenders are worth factoring in when they are offered. Legal fees for a remortgage typically run £500 to £900, and a valuation fee varies by property value. If a lender offers both, that may offset a slightly higher rate on a smaller loan.

Limited Company vs Personal Name Borrowing

There are two structures for holding a buy-to-let mortgage: in your personal name or in a limited company (typically a Special Purpose Vehicle, or SPV).

Personal name: More lenders operate in this market, so product choice and competition are greater. Rates are generally lower. The disadvantage for higher-rate taxpayers is Section 24: you cannot deduct mortgage interest from rental income directly, only claim a 20% basic-rate tax credit.

Limited company: The company deducts mortgage interest in full as a business expense before calculating Corporation Tax. This is the main reason higher-rate landlords use SPVs. The trade-off is a smaller product range, higher arrangement fees, and rates that run approximately 0.3% to 0.8% higher than equivalent personal name products. You also need a personal guarantee as a director in most cases, so the company structure does not eliminate your personal liability on the mortgage.

The tax saving from full mortgage interest relief in a company usually outweighs the higher borrowing cost for higher-rate taxpayers, especially on larger loans or portfolios. The crossover point depends on the loan size, the rate differential, and your personal tax situation. A specialist tax adviser and a whole-of-market broker who covers both personal and company products can model the numbers for your portfolio.

For more on the tax comparison, see our guide to buy-to-let limited companies. For a full list of deductible expenses in both structures, see the allowable expenses for landlords guide.

Portfolio Landlord Assessment

From September 2017, lenders are required to carry out a more detailed background portfolio assessment for applicants who own four or more mortgaged properties. This is known as the portfolio landlord test.

Lenders apply their ICR requirements across the entire portfolio, not just the new property. If your existing properties are highly leveraged, the new application may fail even if the individual property stacks up. Some lenders have stricter portfolio policies than others.

If you are buying your fourth or subsequent mortgaged property, speak to a broker who handles portfolio landlords before applying, as direct applications can result in declined decisions that affect your credit file. If this is your first rental property, the first-time landlord checklist covers the legal obligations you need to have in place before tenants move in.

When to Use a Whole-of-Market Broker

The BTL mortgage market is broader and more specialist than the residential market. Many competitive products are not available directly from lenders and are only accessible through intermediaries (brokers).

A whole-of-market broker has access to the full market, including specialist lenders who only deal with brokers and who may offer better terms for specific circumstances such as HMOs, limited companies, holiday lets, or portfolio landlords. They also know which lenders apply the strictest criteria and can identify the most likely approval before you apply, protecting your credit file from unnecessary hard searches.

Broker fees vary. Some charge a flat fee (typically £500 to £1,500), others take a commission from the lender (typically 0.3% to 0.5% of the loan), and some operate a combined model. On a £200,000 mortgage, the difference between an average and an optimal product over five years frequently exceeds the broker fee by a large margin.

Brokers regulated by the FCA are required to recommend the most suitable product for your circumstances. Look for brokers with whole-of-market access and specific BTL experience.

Key Questions for Your Mortgage Comparison

Before selecting a product, confirm answers to these:

What is the total cost over the initial term? Monthly payments multiplied by term length, plus all fees. This is more useful than the headline rate alone.

What are the early repayment charges? If there is any chance you will need to exit the fixed term early, for example to sell or substantially remortgage, understand the ERC structure before you commit.

What is the reversion rate? The SVR the mortgage reverts to at the end of the fixed period. This tells you the urgency of remortgaging before the reversion kicks in.

Does the lender impose a maximum number of properties? Some mainstream lenders cap the number of BTL properties they will lend against, which affects portfolio landlords.

What are the overpayment allowances? Most fixed-rate BTL mortgages allow 10% overpayment per year without penalty. If you want to reduce the outstanding balance, confirm the overpayment terms.

What is the interest-only policy? Most BTL mortgages are interest-only by default. If you want a repayment product, confirm it is available and at what cost.

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This guide contains general information about buy-to-let mortgages. It does not constitute financial or mortgage advice. Buy-to-let mortgages are not regulated by the Financial Conduct Authority for the purposes of most investment purchases. Always speak to a qualified whole-of-market mortgage broker before making borrowing decisions. Your property may be repossessed if you do not keep up repayments on a mortgage.