Let to Buy Mortgages. What They Are and How They Work

Moving home does not always mean selling your current property. If you have built up equity in your existing home and the local rental market is strong, letting out your current property while purchasing a new one — known as let-to-buy — can be an attractive option. It allows you to keep an investment asset while still upgrading or relocating to a home that better suits your needs. In this guide, we explain how let-to-buy works, the different routes available, the costs involved, and the key considerations before making this decision.

What Is Let-to-Buy?

Let-to-buy is essentially the reverse of buy-to-let. Instead of buying a new property to rent out, you keep your existing home and let it out to tenants, while taking out a new residential mortgage on the property you are moving to.

The concept is straightforward, but the financial and legal arrangements require careful planning. You effectively end up with two mortgages: a buy-to-let (or consent-to-let) arrangement on your existing home, and a new residential mortgage on your new home.

Let-to-buy is popular among homeowners who are moving home for a variety of reasons:

• Relocating for work — if your job takes you to a different area, letting your current home provides income and a safety net if you ever return
• Upsizing for a growing family — rather than selling your starter home, you keep it as an investment and buy a larger property
• Testing a new area — if you are unsure about a permanent move, letting your existing home gives you the flexibility to return
• Building a property portfolio — let-to-buy can be the first step towards becoming a landlord, using a property you already know and understand

Consent to Let vs Buy-to-Let Conversion

There are two main routes to letting out your existing property, and understanding the difference is crucial:

Consent to let — this is where you ask your existing residential mortgage lender for permission to let the property while keeping your current mortgage in place. Some lenders will grant consent to let for a temporary period (usually 12 to 24 months), sometimes with a small increase in interest rate. This is typically the simpler and cheaper route, as it avoids the need to remortgage entirely. However, not all lenders offer consent to let, and those that do often impose conditions, such as requiring you to have owned the property for a minimum period.

Switching to a buy-to-let mortgage — if your lender does not offer consent to let, or if you plan to let the property on a long-term basis, you will need to remortgage onto a dedicated buy-to-let product. This involves a full application assessed on the rental income the property will generate, and you will need to meet the lender’s buy-to-let criteria, including the Interest Coverage Ratio (ICR) requirements. Buy-to-let rates are typically higher than residential rates, and you may need to pay arrangement fees and legal costs. Use our remortgage calculator to compare different options.

The route you choose depends on your lender’s policies, how long you plan to let the property, and the financial implications of each approach. At Option Finance, we can assess both options and advise on the most cost-effective solution for your circumstances.

How Does the Affordability Assessment Work?

One of the trickiest aspects of let-to-buy is passing the affordability assessments for both the letting arrangement on your existing home and the new residential mortgage on the property you are buying. Here is how lenders typically approach this:

For the let property — if you are switching to a buy-to-let mortgage, the lender will assess affordability based on the expected rental income. Most lenders require the rent to cover at least 125% to 145% of the mortgage payment at a stressed interest rate (typically 5.5% or higher). If the rental income does not meet this threshold, you may need a larger deposit or a lender that uses top-slicing (taking your personal income into account alongside the rent).

For the new residential property — the residential mortgage lender will assess your personal income and outgoings in the usual way. However, they will also take into account your existing buy-to-let mortgage commitment. Some lenders offset the rental income against the buy-to-let mortgage payment, while others simply add the full buy-to-let payment to your committed expenditure. The approach used can significantly affect how much you are able to borrow for your new home. Use our affordability calculator to get an initial indication.

Cross-lender coordination — ideally, you want to find lenders for both the buy-to-let and residential mortgages who take a favourable view of let-to-buy arrangements. Some lenders specialise in this area and have more flexible criteria. This is where working with a whole-of-market broker makes a significant difference, as we can identify lenders whose criteria work in your favour across both applications.

Costs Involved in Let-to-Buy

Let-to-buy involves costs on both the letting side and the purchasing side, so it is important to budget carefully:

Stamp duty on the new purchase — because you will own two properties at the point of purchasing your new home, you will need to pay the additional property surcharge of 5% on top of the standard stamp duty rates. This applies even if you intend the new property to be your main residence. For example, on a £350,000 purchase, the stamp duty would be approximately £22,500 with the surcharge, compared to around £5,000 without it. Calculate your exact liability using our stamp duty calculator.

Stamp duty refund — if you sell your previous main home within three years of purchasing the new property, you can claim a refund of the additional 5% surcharge. This is an important consideration if you are undecided about whether to keep the original property long term.

Buy-to-let mortgage costs — if you are remortgaging to a buy-to-let product, expect arrangement fees of £995 to £1,999, valuation fees, and legal costs. There may also be early repayment charges on your existing residential mortgage if you are still within a deal period.

New residential mortgage costs — standard purchase costs apply, including arrangement fees, valuation fees, conveyancing costs, and any broker fees.

Landlord costs — once you are letting your property, you will need landlord insurance, an Energy Performance Certificate (EPC), gas safety certificate, Electrical Installation Condition Report (EICR), and potentially letting agent fees of 8% to 15% of the monthly rent if you use a management service.

Tax on rental income — rental profits are taxable at your marginal income tax rate. Since April 2020, mortgage interest on buy-to-let properties is no longer deductible as an expense but instead qualifies for a 20% tax credit. This particularly affects higher-rate taxpayers.

Key Considerations Before Choosing Let-to-Buy

Before committing to a let-to-buy arrangement, consider the following carefully:

Can you afford both mortgages? — even with rental income, you need to be comfortable managing two mortgage payments. What happens if the property is empty between tenants (a void period)? Could you cover both payments from your personal income for a few months if necessary? Our mortgage calculator and repayment calculator can help you model different scenarios.

Is the rental yield sufficient? — research the local rental market to understand achievable rents. A letting agent can provide a rental valuation, and online portals can give you an idea of comparable rents in the area. The rental income needs to cover the buy-to-let mortgage payment and contribute towards ongoing costs.

Are you prepared to be a landlord? — letting a property comes with legal responsibilities, including maintaining the property to habitable standards, protecting the tenant’s deposit in a government-approved scheme, complying with safety regulations, and handling repairs promptly. Consider whether you want to manage the property yourself or appoint a letting agent.

What is your long-term plan? — are you keeping the property as a long-term investment, or is this a temporary arrangement while you decide whether to sell? Your answer affects which mortgage route to take and how you structure the arrangement.

What about capital gains tax? — if you eventually sell your original home after letting it out, you may face a capital gains tax (CGT) liability on any gain during the period it was not your main residence. Private Residence Relief covers the period it was your main home plus the final nine months of ownership, but any remaining period is subject to CGT at 18% (basic rate) or 24% (higher rate). The current annual CGT allowance is £3,000 per person. Understanding the CGT implications before you start letting is important for your long-term financial planning.

Let-to-Buy for First-Time Landlords

If you have never been a landlord before, the prospect of letting out your home can feel daunting. Here are some practical tips:

• Get a proper rental valuation — do not guess what rent to charge. Get valuations from at least two local letting agents and check comparable properties online
• Choose the right tenancy agreement — most residential lettings in England use an Assured Shorthold Tenancy (AST), which gives both parties clear rights and obligations
• Protect the deposit — you are legally required to protect your tenant’s deposit in one of the three government-approved tenancy deposit schemes within 30 days of receiving it
• Budget for maintenance — a good rule of thumb is to set aside 10% to 15% of rental income for repairs and maintenance
• Consider a letting agent — a full management service handles tenant finding, rent collection, maintenance, and compliance for a fee. This is particularly useful if you are moving a significant distance from the property
• Inform your insurance provider — standard home insurance does not cover a let property. You need specialist landlord insurance covering buildings insurance, landlord liability, and ideally rent guarantee and legal expenses

If you already have experience with property and are thinking about expanding further, our guides on buy-to-let and commercial mortgages cover more advanced options.

Mortgage and Tax Implications of Let-to-Buy

Beyond the immediate costs, let-to-buy has longer-term financial and tax implications that you should factor into your decision:

Income tax on rental profits — the rental income you receive after letting your property is taxable. You will need to register for self-assessment with HMRC and file an annual tax return declaring your rental profits. Allowable deductions include letting agent fees, insurance premiums, maintenance costs, and a 20% tax credit on mortgage interest payments.

Capital gains tax on future sale — if you sell your former home after it has been let out, you may face a capital gains tax liability. Private Residence Relief covers the period the property was your main home plus the final nine months of ownership. Any remaining period when the property was let is subject to CGT at 18% (basic-rate taxpayers) or 24% (higher-rate taxpayers), with a current annual exemption of £3,000 per person. Letting Relief of up to £40,000 is available only if you shared occupation of the property with a tenant.

Mortgage interest deductibility — since the restriction on mortgage interest relief for individual landlords, higher-rate taxpayers can no longer deduct their full mortgage interest as a business expense. Instead, all landlords receive a 20% tax credit. This affects the net profitability of the letting arrangement and should be factored into your financial modelling.

It is strongly advisable to discuss the tax implications with a qualified accountant before committing to a let-to-buy arrangement.

How Option Finance Can Help With Let-to-Buy

Let-to-buy involves coordinating multiple financial products and navigating different lender criteria for both the buy-to-let and residential sides of the arrangement. Getting this right requires whole-of-market knowledge and an understanding of how different lenders assess these applications.

At Option Finance, our experienced advisers handle let-to-buy arrangements regularly. We can:

• Assess whether consent to let or a buy-to-let remortgage is the better route for your existing property
• Identify residential lenders who take a favourable view of let-to-buy applicants
• Coordinate both applications to ensure they progress smoothly
• Advise on stamp duty implications, including the potential for a surcharge refund
• Help self-employed applicants and those with adverse credit navigate the additional complexities these situations can bring

Whether you are a first-time buyer stepping into landlord territory for the first time or an experienced property owner, we are here to guide you through every step of the process. Apply now to speak with one of our advisers and explore whether let-to-buy is the right move for you.