Written for portfolio landlords, letting and managing agents, HMO operators and short-let operators in England, Wales, Scotland and Northern Ireland.
The short version
- List every loan's end date and reversion rate.Reversion rate means the rate after the fix. Note each early repayment charge. Put payments, rent, repairs and tax dates in a 13-week cash view.
- Start refinancing six months before each fix ends.Brief a mortgage broker then. The end date is known from the day you sign, so only a late start makes it a surprise.
- Test each property against the lender's rent cover.Lenders check rent covers interest at a test rate, with a margin on top. Take both from that lender's criteria, never a rule of thumb.
Most landlords know their rent to the penny. Fewer know the date each fixed rate ends and what the payment becomes after it. When an interest-only buy-to-let loan moves to a higher rate, the payment rises straight away, and an individual landlord paying higher-rate tax gets only basic-rate relief on the rise.
Keep a 13-week cash view
Put the property lines in it: rent by tenant and rent day less the arrears and voids you expect, mortgage payments by lender, agent fees, repairs and compliance due dates, insurance and service charges, and the 31 January and 31 July tax payments. An agency adds fee income and salaries and keeps client money out of its own cash. Hold a repairs and void reserve per unit at a level you choose.
Fix maturities: start 6 months ahead
List each loan's end date, its early repayment charge and the reversion rate it falls to, and start refinancing 6 months before the end date. A mortgage broker covers products, early repayment charges and consent to let, and the offer letter governs.
| Annual interest at 5.00% on £187,500 | £9,375 |
| Less annual interest at 2.50% | -£4,687.50 |
| Extra cost a year | £4,687.50 |
| New monthly payment | £781.25 |
£9,375 / 12, up from £390.63Under section 24 a higher-rate landlord gets only basic-rate relief on the rise.
Will the lender still lend?
Lenders test stressed rent cover with an interest cover ratio (ICR): annual rent divided by the loan multiplied by a stressed rate. Each lender sets its own ICR floor in its criteria, so take the figure from the lender's criteria or offer, never from a rule of thumb. Lenders may also want an HMO licence and planning in place first, and directors' guarantees on company loans.
The stress test lenders apply
For in-scope buy-to-let lending, the lender must assess likely future rates over at least the first 5 years, considering market expectations, a minimum 2 percentage point increase and any FPC direction, and must assume a borrower rate of at least 5.5%. That specific stress does not apply where the rate is fixed or capped for 5 years or more (or for the full contract if shorter), but the lender must still consider refinancing risk and may apply its own affordability tests. As of Oct 2026.
PRA SS13/16 (a lender standard)
| Stressed interest: £187,500 at 5.5% a year | £10,312.50 |
| Plus 25% cover on top | £2,578.13 |
| Annual rent needed at a 125% ICR | £12,890.63 |
| Monthly rent needed | £1,074.22 |
£12,890.63 / 12At a 145% floor the rent needed is £14,953.13 a year (£1,246.09 pcm). The £187,500 loan is 75% of a £250,000 flat; let at £1,250 pcm, it passes both at 5.5%, just. But 5.5% is only the minimum: on a new fix of under 5 years at, say, 5%, a lender applying the 2 point rise would stress at 7% or more, and at 7% the flat needs £1,367.19 pcm even at 125%, so it fails. The 125% and 145% floors are assumptions for this example, not quoted market figures.
The end date is known from the day you sign; only a late start turns it into a surprise.
Check the type of mortgage, not just the rate. Buy-to-let to unconnected tenants is mostly unregulated business lending, letting to a family member is regulated buy-to-let, and letting a home that sits on a residential mortgage needs the lender's consent to let.
Asked in Greymill
Now, at 2.5%: £390.63 a month
At 5%: £781.25 a month
That is £4,687.50 a year more. If you pay higher-rate tax, you get only basic-rate relief on the rise.
Will a lender still lend? Your rent must cover the interest at a stressed (test) rate, plus a margin set by that lender: its floor. On a fix under 5 years, the lender must test at 5.5% or more (As of Oct 2026). Rent needed:
If the floor is 125%: £1,074.22 a month
If the floor is 145%: £1,246.09 a month
Your £1,250 passes both, just: £3.91 to spare at 145%.
The trap: 5.5% is a minimum. The lender must also consider a rise of at least 2 points, so a new short fix at 5% may be tested at 7%. Then you need £1,367.19 a month even at 125%, and fall short. Use that lender's own figures.
Shall I add the new payment to a 13-week cash view?
Ask it about your own business
Paste this into Greymill with your own figures, and Loans & Funding works it through for your business.
I run a property management business in the UK. I own [number] buy-to-let properties in [nation]. For each loan: lender [name], balance [£], rate [%], fix end date [date], early repayment charge [£ or %], reversion rate [%], and rent [£ pcm]. Build me a 13-week cash flow with rent, arrears, voids, mortgage payments, repairs, compliance dates, insurance and tax dates, then a refinance timeline showing each new payment at [assumed rate] and whether each property passes an ICR of [lender's floor] at [lender's stress rate].
More for property management and rentals in the UK
- Our renewal commission has gone: how do we replace it?Since 1 May 2026 English tenancies have no fixed term to renew, so renewal-based fees may stop and the gap has to be priced openly to landlords.Read the lesson
- Section 24 is eating my rental profit: should the properties go into a company?Individual landlords get only a basic-rate credit for mortgage interest, but moving a portfolio into a company can cost more up front than it saves in decades.Read the lesson
- Is every property legal to let? Certificates, alarms, Right to Rent and HMO licencesCostly lettings mistakes are often a missed certificate, check or licence, so run one compliance tracker per property and clear the move-in items first.Read the lesson
- Our tenancy and management agreements were written for fixed termsSince 1 May 2026 several clauses English agreements still carry have no effect and some break the Tenant Fees Act, so check the paperwork before you sign or rely on it.Read the lesson
- Paying negotiators on commission without falling below the minimum wageLow basic pay plus commission can fail the minimum wage in a quiet month, and renewal-based commission has to be retired properly now renewals have gone.Read the lesson
- Winning landlords when there are no renewals left to sellLandlords now buy compliance, lawful arrears handling and evidenced rent reviews, and every advert you run for them has to meet consumer law.Read the lesson
- A tenant has stopped paying: what to do first, nation by nationArrears cases are lost on a missed step, so check the deposit and certificates, log the arrears, and use the right ground for the nation the property is in.Read the lesson
Open the interactive lesson · Every property management and rentals lesson · What Greymill knows about the trade
Sources
The primary sources behind this lesson, checked Oct 2026.
- deadlines (Cash, lending and refinancing)
- Mortgage Credit Directive Order 2015 Part 3 (Cash, lending and refinancing)
- higher rates table (Show the maths and source every figure)
- SS13/16 paragraphs 2.11 to 2.17, especially 2.12 to 2.14 (Show the maths and source every figure)
- main points (Show the maths and source every figure)
- summary (Show the maths and source every figure)
- dates list (Show the maths and source every figure)
- RICS Valuation: Global Standards, PS 1 (Show the maths and source every figure)