Quick Links:
A buy to let remortgage is when you move the mortgage on a rental property you already own onto a new deal, either with your current lender or a different one. The property does not change hands and your tenants stay where they are. All that changes is the loan behind it. Most landlords do it because a fixed rate is ending, and from application to formal offer it usually takes two to three weeks.
If you are letting a home you used to live in rather than a property you bought as an investment, that is usually consumer buy to let, which is regulated differently and worth reading first.
Start looking about six months before your current deal ends, which leaves time to compare properly and line the switch up for the day your fixed rate finishes.
Lenders decide how much you can borrow from the rent rather than from your salary, using an interest coverage ratio.
The Prudential Regulation Authority expects lenders to test buy to let borrowing at a minimum rate of 5.5%, unless the rate is fixed for five years or more.
The two documents that hold cases up most often are the tenancy agreement and proof the rent is actually landing in your account.
Four or more mortgaged buy to let properties makes you a portfolio landlord, so lenders underwrite your whole portfolio, not just the property you are refinancing.
How HTG Mortgages Can Help
I look across the whole market rather than one lender’s range, so the question I am answering is not which of my products fits you, it is which of the 120 or so lenders I work with will take the most sensible view of your rent, your ownership structure and the rest of your portfolio. That matters more on buy to let than it does on a residential mortgage, because lenders differ a lot in how hard they stress the rent and what they will accept as proof of it. My fee is a flat £350, payable when your mortgage offer comes through, with nothing to pay upfront. You can see how that works on my fees page, or read more about the service on my buy to let remortgage page.
What is a buy to let remortgage, and how is it different from a purchase?
The mechanics are simpler than a purchase because there is no chain, no estate agent and nobody moving house. You already own the property, so the new lender is only assessing you, the property and the rent. There is no offer to negotiate and no seller to wait for.
What is not simpler is the lending assessment. On a purchase the lender is looking at a property you are about to own. On a remortgage it is looking at a property with a real tenancy, a real rent and a real payment history attached, and all three of those get checked. If you are buying rather than refinancing, I have written a separate guide to the buy to let mortgage process from application to approval.
When should you start?
About six months before your current deal ends.
That sounds early, and most landlords come to me later than that. The reason for six months is that it gives you time to get an offer in place without any pressure, and then time it so the new mortgage starts the day after your existing deal finishes. Switch before that and you will usually pay an early repayment charge to your current lender, which can wipe out the saving you were chasing. Leave it too late and you drop onto the lender’s standard variable rate while the new application catches up, which is almost always the most expensive rate they have.
A mortgage offer stays valid for a set period once it is issued, and that period varies by lender, so getting one early does not tie you into completing sooner than you want to. Starting early costs you nothing. Starting late costs you a month or two on the standard variable rate.
What actually happens, and how long does it take?
From the point I submit an application, two to three weeks to a formal offer is normal.
Before that there is a first conversation where I go through the property, the rent, how you own it and what you want the new deal to do. Then I research the market and come back to you with what is available and why. Once you are happy, the application goes in, the lender instructs a valuation, and an underwriter reviews the file. That is the two to three weeks.
After the offer there is legal work. A remortgage still needs a conveyancer to redeem the old mortgage and register the new one, and many lenders provide one as part of the deal. This stage is usually where the calendar time goes, not the lending decision. I have written up what the final stage looks like in what happens on remortgage completion day.
What documents will a lender want?
It depends on how you own the property, and the split between personal ownership and a limited company is where most of the difference sits.
If you hold the property in your own name, expect to provide identification and proof of address, the tenancy agreement for the current tenant, bank statements showing the rent arriving, a recent statement for the existing mortgage, and proof of any personal income the lender is taking into account. If that income is self-employed, that usually means SA302s and tax year overviews.
If you hold it in a limited company, you will need all of the property paperwork above plus company accounts, the company’s bank statements, details of every director and shareholder, and confirmation of the company’s SIC codes. Lenders will also normally want personal guarantees from the directors, which catches people out the first time. There is more on how company lending is assessed on my limited company mortgages page.
The point worth taking from that list is that a lender is checking the rent from two directions at once. The tenancy agreement says what the rent is meant to be. The bank statements prove it is actually being paid. You need both.
Speak to an expert
Whether you’re buying your first home, moving house or remortgaging, HTG Mortgages is here to make the process as simple and stress-free as possible. I’ll compare mortgages from over 120 lenders, guide you every step of the way and help you find the right mortgage for your circumstances.
How does the valuation work on a rental property?
The lender instructs a valuation for its own purposes, and on a buy to let the surveyor is asked for two figures rather than one: what the property is worth, and what rent it could realistically achieve on the open market.
That second figure is the one that catches landlords out. If the surveyor’s rental assessment comes in below the rent you are actually charging, it is generally the lower of the two that drives the affordability calculation, and your borrowing comes down accordingly. Surveyors tend to take a cautious view, particularly where a property has unusual features or where the rent sits above the local average.
Not every valuation involves a visit. On a remortgage, lenders will often use an automated or desktop valuation based on local sales data, sometimes a drive-by, and a full internal inspection where the property or the loan is more complex. You do not get to choose which, and a free valuation is usually the automated sort.
What helps is evidence. A current signed tenancy agreement and bank statements showing the rent being paid give a surveyor and an underwriter something concrete to work from, and they give me something to push back with if a figure comes in low.
How does the stress test decide what you can borrow?
Buy to let affordability is worked out from the rent through an interest coverage ratio, which is the rent expressed as a percentage of the monthly interest payment.
The rules behind it come from the Prudential Regulation Authority’s supervisory statement SS13/16. It notes the industry standard minimum ratio of 125%, and expects lenders to test the borrowing at a stressed rate rather than the rate you are actually paying: a minimum of two percentage points above the product rate, and never less than 5.5%, assessed over at least the first five years of the loan.
There is one significant carve-out. Where the rate is fixed for five years or more, the lender does not have to apply that stress in the same way, because your payment is fixed for the period being assessed. That is why a five-year fix often allows more borrowing than a two-year fix on identical numbers. Whether the longer lock-in is right for you is a different question, and it turns on how long you plan to hold the property, whether you might sell or release equity in the meantime, and what an early repayment charge would cost you if your plans change. That is a conversation, not a rule.
Many lenders apply a higher ratio, commonly 145%, where the landlord is a higher rate taxpayer, because the PRA expects the tax cost of the borrowing to be taken into account. Limited company borrowing is often assessed at a lower ratio for the same reason.
For context on how much headroom most landlords actually have, UK Finance reported an average interest coverage ratio of 221% on new buy to let lending in the first quarter of 2026, up from 204% a year earlier, on an average rate of 4.71%. The typical landlord clears the test with room to spare. If you want to see roughly where you stand before we speak, I have two calculators: one for the maximum mortgage your rent supports and one for the rent needed for a given loan.
What changes if you are a portfolio landlord?
Four or more distinct mortgaged buy to let properties makes you a portfolio landlord under the PRA’s definition, and it changes the assessment considerably.
SS13/16 expects lenders to use a specialist underwriting approach for portfolio landlords, and to take account of your experience as a landlord, your full portfolio and the mortgages outstanding on it, your assets and liabilities including tax, the merits of the new borrowing in the context of the existing portfolio and your business plan, and the historical and expected cash flows across all of your properties.
In practice that means paperwork. Lenders typically ask for a full portfolio schedule, a statement of assets and liabilities, a business plan, cash flow figures and bank statements, and they will run a background stress test across the whole portfolio and calculate an overall loan to value, not just the numbers on the one property you are refinancing. A property elsewhere in the portfolio that is sitting empty, or carrying more debt than its rent supports, can affect an application on a completely different property.
None of that is a problem if it is prepared properly, but it is why a portfolio remortgage needs starting earlier than a single-property one. There is more background on what a portfolio landlord is.
What if you are letting a home you used to live in?
This is the group I would most like to reach with this article, because it is where people get it wrong through not knowing rather than through carelessness.
If you moved out of a property and let it, or you inherited one and rented it out, you are a landlord whether or not you ever planned to be. Letting a property that still has a residential mortgage on it, without telling the lender, breaches the mortgage terms. Lenders can and do respond by putting the rate up and backdating the difference.
The proper routes are consent to let or a buy to let remortgage. Consent to let is formal permission from your existing lender to let the property while keeping your residential mortgage. It is normally time-limited rather than permanent, lenders may charge an administration fee or add a loading to your rate, and it is designed for temporary situations. If you are letting the property for the foreseeable future, a buy to let mortgage is the arrangement that actually matches what you are doing.
There is a regulatory wrinkle here too. Most buy to let lending is not regulated by the Financial Conduct Authority, because it is treated as business lending. But where a borrower is not acting wholly or predominantly for business purposes, which is often the case for someone who did not set out to be a landlord, the loan can fall under the separate consumer buy to let regime introduced by Part 3 of the Mortgage Credit Directive Order 2015 and in force since 21 March 2016. Firms have to be registered with the FCA to arrange those. It is worth knowing that the protections attached to your mortgage may not be the same as the ones on the residential mortgage you are used to, and it is one of the first things to establish rather than the last.
What slows a buy to let remortgage down?
Missing proof of rental income, and a missing or out of date tenancy agreement. Those two account for most of the delays I see.
It is an easy problem to avoid. Before you start, find the current signed tenancy agreement, check it reflects the rent you are actually charging and the tenant who is actually living there, and pull off three to six months of bank statements showing the rent arriving. If the rent goes through a letting agent, get their statements too. Sorting that out in advance is usually the difference between two to three weeks and six.
Where to start
If your buy to let deal ends within the next six months, the useful thing to do now is find out what your rent supports at today’s stress rates, before you are up against a date. That is a short conversation and it costs nothing.
You can read more about buy to let lending generally on my buy to let mortgage hub. I am a whole of market broker based in Winchester and I work with landlords across Hampshire and the rest of the UK.
Information correct as of August 2026. The Financial Conduct Authority does not regulate most buy to let mortgages. Tax treatment depends on your individual circumstances and may change, so speak to an accountant about the tax side of any decision.
The rate you are offered on a remortgage is shaped partly by swap rates, which move on inflation data like July’s UK inflation figures.
Need Personal Mortgage Advice?
Every buyer’s situation is different. While this guide explains the general rules, the right mortgage for you depends on your income, deposit, credit history and future plans. If you’d like tailored advice, I’m here to help, with whole-of-market coverage.
