When Your Buy-to-Let Fixed Rate Ends: Product Transfer or Remortgage?
The most expensive decision in a buy-to-let is often the one nobody makes. The fixed rate ends, nothing is arranged, and the mortgage quietly moves onto the lender's standard variable rate — which is rarely a rate anyone would choose.
There are three things that can happen when a fix ends. Two of them are decisions. This guide is about making one of those two, early enough that the third never happens.
The three outcomes
| What it is | Effort | Typical cost | |
|---|---|---|---|
| Do nothing | The loan reverts to the lender's standard variable rate (SVR) | None | Usually the highest rate available to you |
| Product transfer | A new deal with the same lender, same loan | Low | Product fee; often no valuation or legal work |
| Remortgage | A new loan with a different lender, repaying the old one | Higher | Product fee, possibly valuation and legal fees — though many deals include these |
What doing nothing actually costs
Take an interest-only buy-to-let with £125,000 outstanding, coming off a 5.00% fix onto an SVR of 7.99%. The SVR is illustrative — check your own lender's — but the gap is typical.
| Monthly interest | |
|---|---|
| On the 5.00% fix | £520.83 |
| On a 7.99% SVR | £832.29 |
| Difference | £311.46 a month |
Three months of drift while you get round to it costs £934.38. That is often more than the product fee on a new deal, and on many properties it is more than the entire monthly cash flow. The cash flow guide explains why that second comparison is the one that matters.
Most SVR loans carry no early repayment charge, so moving off one quickly is usually possible. But "quickly" still means weeks, and the extra interest runs every day of them.
Product transfer: the easy route
A product transfer moves you onto a new rate with your existing lender. Because the loan is not changing, most lenders do not re-underwrite it in full.
- Usually no new affordability test. This matters if your rent has not kept pace with rates — you may pass a product transfer where you would fail a remortgage.
- Usually no valuation and no solicitor.
- Fast. Often arranged online or through a broker in days.
- Bookable early. Most lenders let you choose a product somewhere between three and six months before the fix ends, with the new rate starting the day after.
The trade-off is choice. You are limited to one lender's range, which may not be the cheapest in the market, and you cannot use it to borrow more or release equity on the same terms.
Remortgage: more choice, more scrutiny
A remortgage replaces the loan with a new lender's. You get the whole market to choose from, and the chance to change the loan amount. In return, the new lender underwrites you from scratch.
The rental cover test
Buy-to-let lenders mostly lend on what the property earns, not what you earn. The test is the interest cover ratio: the rent must cover the mortgage interest by a set margin, calculated at a stress rate that can be higher than the rate you will actually pay.
Common ratios are 125% for basic-rate taxpayers and limited companies, and 145% for higher-rate taxpayers. Stress rates vary by lender and by product — five-year fixes are often tested at or close to the pay rate, shorter fixes at something higher.
Here is what that means for the maximum loan on a property renting at £1,050 a month:
| Cover ratio | Stress rate 5.50% | Stress rate 7.25% |
|---|---|---|
| 125% | £183,273 | £139,034 |
| 145% | £157,994 | £119,857 |
The same property, the same rent, and a maximum loan anywhere between about £120,000 and £183,000 depending on your tax band and the lender's stress rate. If your outstanding balance sits near the bottom of that range, a remortgage may simply not be available — and the product transfer becomes the option, not merely the easy one.
These are illustrative figures. Lenders publish their own criteria, and a broker will know which ones are currently lenient. The financing guide covers how lenders read a portfolio more generally.
The other things a remortgage checks
- A fresh valuation. If values have fallen, your loan-to-value may have risen into a worse pricing band.
- Your portfolio. Landlords with four or more mortgaged properties are usually assessed as portfolio landlords, with the whole portfolio's performance under review.
- Your records. Tenancy agreements, rent received, sometimes a business plan. Easy if they exist; slow if they do not.
How to choose between them
- Compare the total cost over the fixed period, not the headline rate. A lower rate with a £1,999 fee can cost more than a higher rate with no fee on a small loan.
- Check whether you would pass a remortgage at all. If the rent does not clear the cover test, the decision is made.
- Decide whether you need to change the loan. Releasing equity or reducing the balance points to a remortgage.
- Weigh the admin. On a small balance, a few basis points of saving may not be worth a full application.
A broker can search the whole market, including product transfers where they have access. Paying a broker fee to avoid months of SVR is usually money well spent.
The timeline that avoids the SVR
| When | What to do |
|---|---|
| 6 months before the fix ends | Find the exact end date and early repayment charge schedule. Check current rent against the cover test. Speak to a broker. |
| 3–6 months before | Book a product transfer, or apply for a remortgage — a remortgage offer typically stays valid for around six months, so an early application is not wasted. |
| Final month | Confirm the new deal starts the day after the old one ends. Check the first new payment on your statement. |
Watch the early repayment charge. Remortgaging a few weeks before the fix ends can trigger a charge worth several months' interest. Most lenders allow a product transfer to start precisely on the end date; with a remortgage, the completion date has to be managed.
Frequently asked questions
Is a longer fix always safer?
It is more predictable, not always cheaper. A five-year fix protects your cash flow from rate rises, but carries larger early repayment charges if you need to sell or refinance in that time. Match the fix to how long you expect to hold the property on the same terms.
Should I switch from interest-only to repayment?
Repayment builds equity but raises the monthly payment substantially, often turning positive cash flow negative. See stress-testing your rental for what that does to the numbers.
Does the new rate change my tax?
Yes — the interest figure feeds your tax credit. Higher interest means a larger credit, but because relief is restricted to the basic rate, the extra cost is never fully offset. Mortgage interest and your tax bill explains the mechanics.
Can I product transfer if I am in arrears?
Often not, or not onto the best rates. Lenders generally want the account up to date. Speak to the lender before the fix ends if payments have been missed.
Know your end dates before the letters arrive
Lenders do write before a fix ends, but the letter tends to arrive late, and it lands in the same pile as everything else. The landlords who never touch an SVR are the ones who track the end date themselves.
The Rental Property Tracker holds each property's loan, rate, term and monthly payment alongside the rent, so you can see what a new rate does to cash flow before you commit to it. Up to twenty properties, $27 once.
General information for UK landlords, not financial or mortgage advice. Lender criteria, stress rates and cover ratios change frequently; figures above are illustrative. Speak to a qualified mortgage broker before acting. Last reviewed September 2026.