Let to Buy Mortgages: How the Two-Loan Move Actually Works

Let to buy is one of the most misunderstood moves in property finance, because it looks like a single decision (keep my home, buy the next one) but runs on two separate mortgages that live under two different rulebooks. Get the structure right and you can fund an onward deposit from equity you already hold. Get it wrong and you either stall the whole chain or, worse, ask the wrong kind of firm to arrange the wrong kind of loan.

This guide is written for the owner-occupier who is about to become a landlord, deliberately or by circumstance. It explains what let to buy actually is, how the two loans fit together, where the regulated line sits (the part most guides skate over), how much deposit a remortgage can realistically release, and the point at which letting your old home quietly turns you into a property business with its own tax profile. It is a finance-mechanics page. The tax decisions are summarised and linked to our detailed guides, not re-argued here.

What let to buy actually is

Let to buy is the arrangement that lets you move house without selling. You keep the home you currently own and live in, put it on rent, and buy a new home to move into. People arrive here for two reasons. Some are deliberate: they want to start a rental portfolio and their existing home, already owned and already in a decent area, is the obvious first asset. Others are reluctant: a sale has fallen through, the market is flat, or they simply cannot bear to sell a home they think will keep rising, so they let it and move on.

The distinction between deliberate and reluctant is not just a mood. It decides which regulatory regime your rental loan falls under, and therefore who is allowed to arrange it. Hold that thought, because it runs through everything below.

What let to buy is not is a product you can walk into a branch and ask for by name. There is no single "let to buy mortgage". There are two ordinary mortgages, a buy-to-let remortgage and a residential purchase mortgage, applied for at the same time and made to work together. Understanding them as two things, not one, is the whole skill.

The two moving parts: two loans, two rulebooks

Every let-to-buy plan has the same two components.

• A buy-to-let remortgage on the home you are keeping. This replaces your existing residential mortgage on that property. It is assessed on the rent the property will earn, measured against an interest coverage ratio (ICR), not on your salary. Crucially, it is usually set up to release equity: if the new loan is bigger than the mortgage it clears, the surplus is paid to you in cash.
• A residential purchase mortgage on the home you are buying. This is an ordinary owner-occupier mortgage, assessed on your income and outgoings under normal affordability rules. The cash released from the first loan typically becomes the deposit for this one.

These are not two halves of one facility. They are two contracts, frequently with two different lenders, each underwritten to its own criteria. They often exchange and complete on the same day so the chain holds together, but a stall on one does not automatically move the other. Treating them as a single application is the most common way people underestimate the timeline.

The regulated line: the part most guides get wrong

Here is the point that separates an accurate let-to-buy guide from a broker blog. The two loans do not just have different criteria, they sit on opposite sides of the financial-services regulatory perimeter.

The onward home is regulated. The mortgage on the property you are buying to live in is a regulated mortgage contract, because you or a member of your family will occupy it. That is defined in the Regulated Activities Order 2001, Article 61, and it is consumer home finance supervised by the FCA (see FCA PERG 4.4). Advising on or arranging that loan is a regulated activity. It is not something we introduce, arrange or comment on. If you need that mortgage, speak to an FCA-authorised mortgage adviser.

The retained home is more nuanced than "just a buy-to-let". Because the property you are letting was your home, the remortgage on it is frequently a consumer buy-to-let, not straightforward business lending. A consumer buy-to-let is a rental mortgage the borrower did not enter into wholly or predominantly for the purposes of a business, and letting a former residence is the textbook case. Consumer buy-to-let has its own regime under the Mortgage Credit Directive Order 2015, and only an FCA-registered firm may arrange it. The FCA sets out the business-versus-consumer distinction in PERG 4.10A.

So the retained-property loan is only unregulated business lending, the kind we can make a bare introduction on, where you are genuinely acting as an investor: letting the property as a deliberate step in building a rental business, typically with a plan to hold or expand rather than an accidental one-off. If you are a reluctant landlord letting a former home until the market turns, that is consumer buy-to-let, and it belongs with an FCA-registered adviser, not with us.

Releasing a deposit from the home you keep: a worked example

The financial engine of let to buy is the equity trapped in your current home. A remortgage converts part of it into a usable deposit. Two ceilings decide how much you can release: the loan-to-value cap and the rental stress test. The lower of the two wins.

Take a homeowner with a current home worth £300,000 and an existing mortgage of £150,000. They want to buy an onward home worth £400,000 and need a deposit.

• Loan-to-value ceiling. A buy-to-let remortgage commonly reaches 75% of value, so up to £225,000 on this property.
• Equity released. The new £225,000 loan clears the old £150,000 mortgage and hands back the difference, roughly £75,000 in cash (before fees), which becomes the deposit on the £400,000 onward home.
• The stress test. The £225,000 loan still has to be affordable on rent. Lenders following PRA Supervisory Statement SS13/16 apply an interest coverage ratio, typically 125% for basic-rate or company borrowers, tested at a stress rate around 5.5%. At 5.5% the notional interest on £225,000 is about £1,031 a month, and 125% of that is roughly £1,289. So the property must rent for about £1,289 a month for the full £225,000 to stand up.

If the expected rent is £1,300 a month, it clears, just, and the £75,000 deposit is available. If the rent were only £1,100, the ICR (not the loan-to-value cap) would pull the maximum loan down, the released equity would shrink, and the onward purchase would need topping up from savings. This is why the rent figure, not the property value, is usually the real constraint. You can model your own numbers with our buy-to-let rental stress test calculator and size the remortgage with the buy-to-let mortgage calculator.

The mechanics of pulling equity out by remortgaging are the same ones landlords use to fund their next purchase generally. If your interest is really in recycling capital across a growing portfolio rather than a one-off house move, the wider mechanics are covered in our guides to capital raising by remortgage and equity release and to when buy-to-let refinancing makes sense.

Consent to let versus a let-to-buy remortgage

There is a lighter-touch alternative that is often confused with let to buy: consent to let. It is worth being clear on the difference, because choosing the wrong one can stall your move.

• Consent to let is a temporary permission from your existing lender to rent your home out while keeping your current residential mortgage in place. It suits a short or uncertain let (a secondment, a trial period, a slow market). It is usually time-limited, may carry a rate loading, and almost never allows you to release equity. That last point is decisive: if your onward deposit has to come from your current home, consent to let cannot deliver it.
• A let-to-buy remortgage is the permanent version. You move the property onto a proper buy-to-let (or consumer buy-to-let) mortgage, which is what most lenders expect if you are simultaneously buying and financing a new home. It is the route that releases a deposit and puts the property on a footing built for long-term letting.

As a rule of thumb: if you are keeping the old home for a few months and can fund the new deposit another way, consent to let may be enough. If you are letting for the long term and need the equity, you are in let-to-buy remortgage territory.

Where let to buy quietly becomes a property business

The moment your old home is let, it stops being a home and becomes a rental property, with a tax profile of its own. This is a tax matter, so we summarise it and link the detailed working rather than re-deriving it here.

Three points matter from day one. First, the rental profit is taxable, and if you own the property personally the Section 24 finance-cost restriction means your mortgage interest gives a basic-rate tax credit, not a full deduction. Our page on how BTL mortgages work for tax walks through exactly how that reducer is calculated. Second, when you eventually sell, the years you lived in the property usually attract private residence relief, but the letting years can be chargeable to capital gains tax, so the clock starts the day it is let. Third, if this is the first step in a deliberate portfolio, you may later weigh holding future purchases through a company; the trade-offs are set out in our limited company versus personal ownership tax comparison. You cannot fold your existing mortgaged home into a company as part of the let-to-buy itself, because moving a personally owned property into a company is a sale to that company and triggers its own capital gains tax, stamp duty and a fresh limited-company mortgage.

Costs, timing and the practical sequence

Let to buy carries more moving costs than a straight house move, so budget for them up front rather than discovering them mid-chain.

• Two sets of mortgage costs. Arrangement fees, valuations and legal work on both the buy-to-let remortgage and the residential purchase. Buy-to-let arrangement fees are often percentage-based, so a larger remortgage can carry a meaningful fee.
• The stamp duty surcharge. Because you keep your current home, you own two dwellings at completion on the new one, so the higher rates for additional dwellings normally apply to the purchase (a 5% surcharge in England from 31 October 2024, with different rules in Wales and Scotland; verify the current rate). The relief that removes the surcharge requires you to sell your previous main home, which a let-to-buy specifically does not do. This is frequently the largest single extra cost, so confirm it before you offer on the onward home.
• Sequencing. If the deposit comes from released equity, the remortgage must complete first or on the same day, because you need the cash to buy. Two lenders and two solicitors' timelines have to meet, so allow more time than a single-property move and expect the chain to move at the pace of the slower loan.

If your longer-term plan is a portfolio rather than a single move, our buy-to-let mortgages guide covers how ICR, LTV, lender tiers and personal-versus-company finance fit together across multiple purchases.

Who this page is for, and who to see instead

Let to buy is genuinely useful when you have real equity in a home worth keeping and a clear, deliberate reason to let it. It is a poor fit when the numbers only work by stretching both loans to their limits, or when the "investment" is really an accidental let you would exit at the first chance.

To be precise about our role: we can help with the tax and structure side of the rental property (Section 24, capital gains exposure, deposit efficiency, whether a company fits future purchases), and where the rental leg is genuine business finance we can make a bare introduction to a business-finance broker. We do not, and cannot, arrange or introduce the regulated consumer parts of a let to buy: the mortgage on the home you are buying to live in, or a consumer buy-to-let on a home you are letting reluctantly. Both of those belong with an FCA-authorised or FCA-registered mortgage adviser. Knowing which side each of your two loans falls on is the first thing to settle, and it is where this whole exercise should start.