Guide to Buy to Let Mortgages

Last updated: 11 August 2026

Most guides to buy to let mortgages explain the product and stop. The product is the easy part. What catches landlords out is everything sitting around it: which facility suits which moment, what happens when you own four properties instead of three, and the growing pile of rules a lender now expects you to be complying with before it will lend at all. This guide covers the landlord’s view rather than the borrower’s. The range of products across the life of a portfolio, how lenders treat you as you scale, the compliance layer, and the places people trip.

The Product Range, Not Just the Purchase

A buy to let mortgage is one product in a family, and landlords use most of them eventually. Purchase. The standard case, assessed mainly on the rent the property will produce rather than your salary. Remortgage. Moving an existing rental to a new lender or a new deal, usually at the end of a fixed rate. This is where most landlords lose money quietly, by drifting onto a reversion rate for a few months between deals. Let to buy. Keeping your current home, switching it to a buy to let, and buying a new home to live in. Two applications running together, and a genuinely useful route when selling is either difficult or unappealing. Consent to let. Permission from your existing residential lender to let the property temporarily without changing the mortgage. Fine for a fixed period, not a permanent arrangement, and it usually comes with conditions and sometimes a rate change. Further advances and second charges. Raising money against a property you already own, either from the current lender or behind them, commonly to fund the deposit on the next purchase. Short-term into long-term. Buying something unlettable, refurbishing it with bridging finance and refinancing onto a buy to let once it is fit to let. A standard route for anyone adding value rather than buying ready-made.

How Lenders Size the Loan

Buy to let lending is led by rent, not salary. The lender tests whether the rent covers the mortgage payment by a margin, using a stressed rate rather than the one you will actually pay, and that test usually sets your maximum loan long before the loan to value cap does. Two things follow. First, a low-yielding property in an expensive area may borrow less than a cheaper property with strong rent, whatever your income looks like. Second, the same property can produce noticeably different maximum loans at different lenders, because they stress at different rates and require different coverage. Our buy-to-let page sets out how that assessment works in detail.

Personal Name or Limited Company

The reason this question exists at all is a tax change. Individual landlords can no longer deduct finance costs from rental income in the way they once could, and instead receive a credit at the basic rate. Companies are taxed differently and are not affected in the same way. The practical result is that higher rate taxpayers building a portfolio often buy through a limited company, usually an SPV set up for the purpose, while a landlord with one property and modest income may be perfectly well off in their own name. Company lending has a narrower lender pool and slightly higher rates, and moving property you already own into a company is a sale with the costs that implies. This is a tax question with a lending consequence, not the other way round. Take advice on the tax before you decide the structure, then let the structure decide the lender.

What Changes When You Scale

At four or more mortgaged buy to let properties you become a portfolio landlord in the eyes of most lenders, and the application changes character. Instead of assessing one property, the lender assesses the whole portfolio. Expect to provide a property schedule, business plan, cash flow and often your personal tax return. Lenders will look at overall gearing across everything you own, not just the property in front of them, and a portfolio stretched at 80% overall will struggle even where the new purchase looks comfortable in isolation. The landlords who find this stage easy are the ones who keep a current schedule, know their aggregate loan to value and can explain their strategy in two sentences. The ones who find it painful are the ones assembling six years of paperwork in a fortnight.

The Property Matters as Much as the Mortgage

Two properties at the same price can be entirely different lending propositions, and the difference rarely shows up in the estate agent’s listing.

Yield decides how much you can borrow, because the rent drives the calculation. A flat producing 4% gross in an expensive city will borrow less than a terrace producing 8% somewhere cheaper, whatever your own income is. That does not automatically make the higher yield the better buy, since capital growth and tenant demand matter too, but it does mean the two need funding differently.

Some property types narrow the lender list sharply. Flats above shops or takeaways, ex-local authority blocks, high rise without a lift, non-standard construction, studios below a minimum size, and anything with a short lease all reduce the number of lenders willing to look. None of it is unfundable, but the pricing reflects the smaller market, and the time to discover it is before you offer rather than after the valuation.

Lease length in particular catches people. A flat with fewer than about seventy years left will fail with many lenders, and extending the lease is a negotiation with a cost attached that belongs in your purchase budget.

The Costs Landlords Underestimate

The mortgage payment is the predictable part. The rest of it is where the return quietly disappears.

Voids. A property empty for a month a year costs you roughly 8% of the annual rent, and the mortgage does not pause while you find a tenant.

Management. A letting agent handling the property fully will typically take a percentage of the rent every month, and tenant find alone still carries a fee.

Maintenance and compliance. Annual gas safety, periodic electrical inspection, alarms, and the ordinary run of repairs. Older properties eat more.

Licensing fees. Where a scheme applies, the licence runs to hundreds of pounds and needs renewing.

Bringing the property up to standard. Energy efficiency work on an older property is the one most often left out of the sums entirely.

Build these into the appraisal before you buy, and the stress test stops being an obstacle and starts being a reasonable sanity check.

The Compliance Layer

Lenders increasingly care whether you are running the properties properly, because a landlord in breach is a risk to their security. Licensing. Mandatory licensing applies to larger houses in multiple occupation, and many councils operate additional or selective licensing schemes covering ordinary rentals in defined areas. Schemes vary enormously between neighbouring councils, so check with the specific authority before you buy rather than after. Energy performance. There is a minimum EPC standard for letting, and the standard has been under review with proposals to raise it. Check what applies now, and factor the cost of getting an older property up to standard into the purchase price rather than treating it as a surprise later. Safety and deposits. Gas and electrical safety certification, smoke and carbon monoxide alarms, and tenancy deposits protected in an approved scheme. None of it is optional, and a lender’s solicitor may ask.

Where Landlords Get Caught Out

Moving into your own rental. Living in a property mortgaged as a buy to let breaches the terms. If circumstances change, speak to the lender about switching rather than simply moving in. Letting on a residential mortgage. The reverse problem, and the reason consent to let exists. Letting to family. Renting to a close relative is regulated buy to let, a different product from a smaller group of lenders. It is not the same as a standard buy to let, whatever the rent. Short-term and holiday letting. A standard buy to let mortgage generally does not permit it. Holiday lets are assessed on seasonal income and need their own product. Letting the deal lapse. Reversion rates are expensive and the cost compounds across a portfolio. Diarise every expiry.

The Clever Way to Build a Portfolio

One buy to let is a product decision. Five is a strategy, and the lender you use for the second purchase affects what you can do with the fourth. That is where a broker earns their keep: keeping your overall gearing where lenders want it, spreading properties across lenders so no single funder can hold your portfolio hostage, and getting the structure right before it is expensive to change. Tell us what you own, what you are buying and how you hold it, and we will come back within 24 business hours with a straight answer on what is achievable and which lenders fit. Send it over and do the Clever thing. Most buy to let mortgages are not regulated by the Financial Conduct Authority. We are not tax advisers, and tax treatment depends on your circumstances and current rules. Your property may be repossessed if you do not keep up repayments on your mortgage or any other debt secured on it.