Mortgage Consent for Short Lets: What Buy-to-Let Lenders Expect
Many London landlords start short letting without checking the mortgage. That is a risky order of events. A buy-to-let or residential mortgage is a contract with conditions, and letting to guests may breach them.
This guide explains how lenders think about short lets, the three main mortgage routes, what you should ask, and what can go wrong if you let without permission.
Quick answer: Most buy-to-let mortgages assume a long tenancy to one household. If you want to short let, you need your lender’s written consent or a mortgage that allows it, such as a specialist short-let or holiday let product. Do not list the property until you have it in writing.
Why lenders care about how you let
A lender’s decision rests on risk. A standard buy-to-let mortgage is priced and assessed on the assumption of a long-term tenant paying rent under a standard tenancy. Short lets bring different risks: more changeovers, variable income, more wear and tear and more regulatory exposure, particularly in London.
Because of that, many mainstream lenders either prohibit short lets or only allow them with prior consent. The terms are in your mortgage offer and conditions, so read them, and ask your broker if they are unclear.
The three main routes
Lenders and brokers usually talk about three routes. The details vary by lender, so use these as a framework, not a promise.
Consent to let
If you hold a residential mortgage and want to let the property, your lender may grant consent to let. It is usually temporary, often for a year or two, and conditional. It is normally intended for a landlord with a short-term reason to let, not a long-term short-let business. The lender may charge a fee, set conditions or increase your rate. Some lenders cap the number of nights you can let or require you to occupy the property yourself for part of the year.
Buy-to-let mortgage
A buy-to-let mortgage is designed for rental properties. Standard products assume a long tenancy, and affordability is assessed on the expected rent, often through a rental cover test. Some lenders permit a limited number of short-let nights. Others lend on short lets only through specialist products. Always ask in writing what is allowed.
Holiday let or short-let mortgage
A holiday let mortgage is designed for properties let to short-stay guests. The lender assesses affordability using historic or projected short-let income. Deposits are often 20% to 30% and rates are typically higher than standard buy-to-let. These products usually expect the property to operate legally, which in London means complying with the 90-night rule.
Summaries of these routes are available from specialists such as STR Specialist and law firms such as Kingsley Napley.
How lenders assess affordability
For standard buy-to-let, lenders commonly use a rental cover test: the expected rent must be a set percentage above the mortgage interest cost, often in the region of 125% to 145% depending on the lender and your tax position. For short lets, some specialist lenders assess a projection of short-let income, while mainstream lenders may base the test on a standard tenancy rent even if you intend to short let.
This matters because it affects how much you can borrow and which products are open to you. A broker who understands short lets can place you with a suitable lender. Use a mortgage adviser who is authorised and regulated, and ask them to confirm the lender’s position in writing.
Why the 90-night rule matters to lenders
London’s planning rule limits whole-home short lets to 90 nights a year without planning permission. Lenders and insurers expect borrowers to comply with the law, so a plan that depends on more than 90 short-let nights in London without permission may be difficult to finance. Our guide to London’s 90-night rule explains what counts.
A mix of short stays and longer corporate lets of 90 nights or more is often easier to explain to a lender than a full-time nightly operation. Our guide to corporate lets in London explains how the structure works. Also check your lease, because a leasehold flat may have its own restrictions. See our guide to short letting a leasehold flat.
What can go wrong if you let without consent
If you short let in breach of your mortgage terms, you may face:
- Withdrawal of consent or your product, if you exceeded an agreed limit.
- Higher rates or fees.
- A demand to repay, in serious cases, which can be difficult if you cannot refinance.
- Early repayment charges if you have to switch lender.
- Insurance problems, because insurers also expect you to disclose how the property is used. See our guide to short-let insurance.
Lenders cannot be assumed to be flexible. If something goes wrong, your position is far stronger when you can show written consent and a plan that complies with the rules.
Standard tenancies are changing too
If you are weighing short lets against a long let, remember that standard tenancies have changed. Since 1 May 2026 the Renters’ Rights Act has made assured shorthold tenancies periodic. Our guide to the Renters’ Rights Act explains the main changes. If you hold a buy-to-let mortgage, check whether your lender has updated its terms.
Questions to ask your lender or broker
- Does my mortgage allow short lets, and on what conditions?
- Is there a limit on the number of nights or the length of stay?
- Will consent be given in writing, and for how long?
- Will the rate, fee or product change?
- How is affordability assessed for a short let?
- What happens if I move from long lets to short lets, or the other way round?
- Do you need to see my lease, insurance or planning position?
A sensible order of steps
- Read your mortgage terms.
- Speak to a regulated broker about short-let options.
- Get written consent or a suitable product.
- Check your lease and insurance.
- Plan your calendar around the 90-night rule.
- Only then, list the property.
At Corporate Stays we ask for the mortgage position before we take on a property, because an unlicensed short let can create serious problems for the owner. If you want to know what your property could earn within the rules, you can get a free income estimate or message us on WhatsApp.
Frequently asked questions
Can I short let a buy-to-let property?
Only if your mortgage terms allow it. Most buy-to-let mortgages are written for assured shorthold or periodic tenancies to one household, not nightly guests. Ask your lender or broker for written permission, or switch to a mortgage that allows short lets.
What is consent to let?
Consent to let is permission from your lender to let a property you have a residential mortgage on, usually for a limited period and under conditions. It is normally intended for a temporary reason, not for a long-term short-let business, and lenders may charge a fee or raise your rate.
What is a holiday let mortgage?
A holiday let mortgage is designed for properties let to short-stay guests. Lenders look at projected or historic short-let income instead of a standard tenancy rent. Deposits and rates are typically higher than for standard buy-to-let.
What happens if I short let without my lender's permission?
You may be in breach of your mortgage conditions. The lender could withdraw your product, charge fees, demand repayment or take action, and your insurance could also be affected. Get written permission first.
Does the 90-night rule affect my mortgage?
The 90-night rule is a planning limit, not a lender rule, but lenders and insurers also expect you to comply with the law. Lenders may also set their own limit on the number of letting days.
This guide is general information, not mortgage, legal or financial advice. Lender terms and criteria change often and vary by lender. Speak to an authorised mortgage adviser before making decisions. Last reviewed October 2026.
Related landlord guides
-
Can You Short Let a Leasehold Flat in London? Lease Checks First
- Short-Let Insurance for London Landlords: What You Need
- The Renters’ Rights Act 2025: What London Landlords Need to Know
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