Interest Cover Ratio (ICR): The Stress Test on Commercial Investment Mortgages in 2026
Every commercial investment mortgage in the UK is underwritten against one question: does the rent cover the interest, not at today’s rate, but at a deliberately worse one. That check is the interest cover ratio, or ICR, and in 2026 it is one of the most common reasons a rent-producing purchase or refinance gets declined. This guide covers the definition, the calculation step by step, the 1.25x to 2.00x band, the 145% rule, and what to do when the numbers fall short. It draws on our full guide to Commercial Mortgages Broker’s stress test guide and sits alongside our DSCR and buy to let stress test pieces.
Commercial mortgages are unregulated lending that sits outside the FCA’s regulated mortgage perimeter, and we do not hold FCA authorisation because the products we arrange are unregulated. Where a case needs regulated advice, we refer it to a regulated firm. Everything below is market commentary and indicative banding, not a quote, an offer or financial advice.
What rental cover means on a commercial investment mortgage
A stress test is a lender’s check that a borrower can keep making payments if conditions deteriorate, above all if interest rates rise well above current levels (Commercial Mortgages Broker knowledge hub, April 2026). On an investment property the income servicing the debt is rent, so the test takes an interest-focused form: the lender checks whether rental income covers the interest payments at a notional stressed rate rather than the rate actually being charged. Some lenders call it the interest coverage ratio; the two terms mean the same thing.
Rental cover is the standard test on rent-producing property because the loan only stays healthy while the rent keeps paying the interest, whatever happens to values or tenants, so the lender tests that relationship with headroom built in. With the base rate held at 3.75% since the December 2025 cut (Bank of England, June 2026) and commercial investment mortgages priced at roughly 6.5% to 8.5% in mid-2026, a stressed rate in the nines is routine, not pessimistic.
The ICR calculation, step by step
The ICR calculation runs in five steps, carried here by one worked example.
- Start with the loan. Say GBP 500,000 on an interest-only basis at an actual rate of 6.5%.
- Set the stressed rate. Lenders typically test at 2% to 3% above the actual rate, or at a minimum floor, often 6.5% to 8%. Here the lender adds 3%: a stressed rate of 9.5%.
- Work out the annual interest at that stressed rate: GBP 47,500.
- Apply the cover multiple. At a 1.30x requirement, the rent must reach GBP 61,750 per annum.
- Compare with the assessed rental income. Rent of GBP 65,000 passes. Rent of GBP 55,000 fails, even though it clears the actual interest bill with room to spare.
That last line is what catches borrowers out: the whole test happens at the stressed rate. The lender is not asking whether the rent covers the mortgage today, but whether it would still cover the interest after rates have moved against you.
The 1.25x to 2.00x band, and what pushes a lender to the top of it
Most commercial lenders require between 1.25x and 2.00x ICR at the stressed rate (Commercial Mortgages Broker knowledge hub, April 2026). Where a case lands within that wide band is driven by how secure the rent looks.
Asset type matters first. Industrial and warehouse property, resilient and quick to re-let, tends to face the least aggressive testing. Offices attract closer scrutiny in the post-pandemic market: a lender may assume a 3 to 6 month void and reduced rent on re-letting, and typically wants stronger cover. High-street retail with weak tenant covenants is tested more conservatively than well-let retail parks, and operational property such as pubs, hotels and care homes is tested on the viability of the business itself, not just the rent roll.
Semi-commercial property sits in the middle: both income streams are tested, the commercial and residential elements may carry different stress rates, and the blended profile is assessed.
The 145% rule in plain numbers
Cover requirements are often quoted as percentages rather than multiples, and 145% is the figure borrowers meet most often. It means the assessed rental income must be 1.45 times the mortgage payment at the stressed rate: if the stressed annual payment is GBP 40,000, the rent must reach at least GBP 58,000.
The percentage convention comes from the buy to let market, where basic-rate structures, including most limited companies, commonly sit at 125% and higher-rate individuals commonly face 145%. Commercial lenders borrow the same shorthand: 130% and 1.30x describe an identical requirement. Our buy to let stress test guide covers the residential side, including the portfolio landlord rules, in full.
ICR or DSCR: which test applies to your mortgage
The interest cover ratio has a sibling, the debt service coverage ratio (DSCR), and the difference is what gets counted on the payment side. ICR tests rent against interest only, which is why it fits interest-only commercial investment mortgages. DSCR tests total income against total debt service, capital repayment included, which is why it fits owner-occupied property and some investment mortgages, with around 1.25x to 1.65x the common band and 1.35x a typical mid-point for owner-occupier trading businesses.
DSCR tests are more demanding than ICR tests because capital repayment sits inside the calculation. In practice, a rent-producing investment on interest-only terms is assessed on ICR, while a trading business buying its own premises on a repayment mortgage is assessed on DSCR. Our DSCR guide works that test through with its own numbers.
How lenders decide what rent to count
The rent in the ICR calculation is the lender’s assessed figure, not automatically the number on the tenancy schedule. Three things feed it. Lease quality: length, break points and remaining term determine how durable the income looks. Tenant covenant: the financial strength of the occupier decides how much weight the rent carries. Rental evidence: if the passing rent sits above what the local market supports, the valuer’s figure is likely to govern.
The same logic offers an opening. If rents are below market, a rent review or lease renewal before applying lifts the income side of the ratio, and evidence of tenant demand strengthens the case (Commercial Mortgages Broker knowledge hub, April 2026).
When the rental cover test fails: what actually moves the answer
A failed ICR is rarely the end of the deal. Three levers move the result.
More equity. A larger deposit cuts the loan, which cuts the stressed interest the rent must cover. Moving from 70% to 60% LTV can turn a fail into a pass on the same property and rent.
A longer fix. Some lenders discount the stress premium on 5 to 10 year fixed rates because the borrower is insulated from rate movements for longer, so the same rent can support more borrowing, a point our guide on how to pass a stress test develops in detail.
A different methodology. Stress testing is not standardised: each lender sets its own stressed rate and cover requirement from internal risk policy, which is why one lender declines a case another approves comfortably. Matching the case to the lender whose calculation suits it is most of what a specialist broker does.
Where the interest coverage ratio sits in the full stress test
ICR is the heart of the affordability assessment on investment property, but only one part of a wider exercise. Lenders also choose between margin, floor and scenario approaches to the stressed rate itself, covered in our stress test rates piece, and weigh red flags such as marginal cover, adverse credit and unrealistic valuations. Behind it all, the FCA does not directly regulate most commercial mortgage lending, but the PRA sets expectations for banks’ commercial real estate lending, and PRA SS13/16 underpins buy to let affordability testing. Every reputable commercial lender applies some form of stress test.
Frequently asked questions
What interest cover ratio do I need for a commercial investment mortgage? Most commercial lenders require between 1.25x and 2.00x at the stressed rate. Where you land depends on the asset, the lease and the tenant: prime, well-let property with a strong covenant sits toward the bottom, secondary assets and weaker covenants toward the top.
My rent covers the mortgage payment easily, so why was my application declined? Because the test does not run at your pay rate. In our worked example, GBP 55,000 of rent clears the actual interest at 6.5% with ease, yet fails a 1.30x requirement at the 9.5% stressed rate, which needs GBP 61,750.
Is the ICR on a buy to let worked out the same way? The mechanics match, but the numbers differ. Many buy to let lenders stress at 5.5% to 7% and require 1.25x to 1.45x, with 125% common for basic-rate and most limited company structures and 145% for higher-rate individuals. Landlords with four or more mortgaged properties are tested across the whole portfolio under PRA SS13/16.
Where to go next
If a rental cover calculation is standing between you and a commercial investment mortgage, the fix is usually structural: more equity, a longer fix, an improved lease or a lender whose methodology fits the case. For the complete picture across DSCR, buy to let, stress rates and bridging, read Commercial Mortgages Broker’s stress test guide, and to talk a live case through, start at Commercial Mortgages Broker. We arrange commercial mortgages from GBP 150,000 to over GBP 25 million across high-street banks, challenger banks and specialist commercial lenders.