What rent do you need to pass the lender's ICR test?
Work backwards from the lender's cover test to the rent you need, step by step, plus the margin worth keeping above that floor and what breaks the sum.
Updated on 24 August 2026
Short answer: how much rent does the test need?
Most people ask what their ICR is at a given rent. Turn the sum around and ask what rent the test needs. On a £136,500 buy-to-let loan, stressed at 5.5% with 145% cover required, the answer is £907 a month.
Minimum monthly rent = £136,500 × 5.5% / 12 × 1.45 = £907
What this reverse calculation does, and what it does not
The reverse calculation gives you one number: the rent floor a loan of a given size demands. A UK buy-to-let lender divides your rent by a notional monthly interest figure. That ratio is the interest coverage ratio, and it has to clear a set percentage. Fix the percentage, and rent becomes the unknown.
Asking it this way puts the answer before the offer. You find out whether the market rent on a property can carry the loan you want, while you can still walk away. Calculate forwards only, from rent to ICR, and you learn the same thing after you have already bid.
The reverse calculation is not a promise of an offer. ICR is one hurdle among several. Loan to value caps the borrowing separately, and so does the lender's view of you, the property type and the tenancy. Passing on rent alone settles nothing else.
The formula, step by step
The ICR formula is rent divided by notional interest. Rewriting it for rent takes two steps and no algebra beyond a multiplication.
First, take the notional interest. Lenders do not use your pay rate here. They apply a stress rate, so the loan is tested against a higher cost of borrowing than the one you signed for.
Notional monthly interest = loan × stress rate / 12
Second, multiply that figure by the required cover. A 145% requirement means the rent must be 1.45 times the notional interest, every month, before costs.
Minimum monthly rent = notional monthly interest × required ICR
Costs never enter this sum. That is a feature of the UK test, not an oversight, and it is why a property can pass the ICR test and still lose money each month.
Worked example on a £136,500 loan
The property here is a two-bed terrace at £182,000 with a £136,500 mortgage, fixed for five years at 5.34%. The lender tests it at a 5.5% stress rate and asks for 145% cover, the level often applied to a higher-rate taxpayer buying in a personal name.
| Input | Value |
|---|---|
| Purchase price | £182,000 |
| Mortgage at 75% LTV | £136,500 |
| Pay rate, five-year fix | 5.34% |
| Stress rate used in the test | 5.5% |
| Required ICR | 145% |
| Notional monthly interest | £626 |
Minimum monthly rent = £626 × 1.45 = £907 Minimum annual rent = £907 × 12 = £10,886
Three levers move that floor: the loan size, the stress rate and the cover required. The table below holds the loan still and moves the other two.
| Test applied | Minimum monthly rent | Minimum annual rent |
|---|---|---|
| 125% cover at a 5.5% stress rate | £782 | £9,384 |
| 145% cover at a 5.5% stress rate | £907 | £10,886 |
| 145% cover at a 6.5% stress rate | £1,072 | £12,864 |
| Figure | Value | What it means |
|---|---|---|
| Minimum monthly rent | £907 | The floor for exactly 145% cover |
| Achievable market rent | £995 | What comparable flats on the street let for |
| Margin above the floor | £88 a month | 9.7% of headroom before the test fails |
| Rent needed at a 6.5% stress rate | £1,072 | £77 above market rent, so the loan shrinks |
Sensitivity is the whole story here. A one-point rise in the stress rate, from 5.5% to 6.5%, lifts the floor by £165 a month. Market rent of £995 clears the first test comfortably and fails the second outright.
What if the lender uses DSCR instead?
DSCR asks a stricter question than ICR. Debt service coverage ratio divides net operating income by the full debt service, so it counts capital repayment and it deducts running costs first. Portfolio and commercial lenders use it; mainstream buy-to-let lending usually does not.
On the same £136,500 loan, taken on capital repayment over 25 years at 5.34%, the payment is £825 a month, or £9,903 a year. Operating costs run at £3,050 a year. A 1.25 DSCR requirement then rewrites the floor entirely.
Minimum annual rent = (£9,903 × 1.25) + £3,050 = £15,429
That is £1,286 a month, against £907 under the ICR test on the identical loan. The gap is not a contradiction. One test measures interest before costs, the other measures everything after them. Check which test applies before you trust a floor, and read interest-only or capital repayment for what the schedule does to the payment itself.
How much margin above the floor?
| Your situation | Margin above the floor | Why |
|---|---|---|
| Let already, rent evidenced by a signed tenancy | 5% to 10% | Little room, but little doubt about the rent |
| Standard purchase with local comparables | 10% to 20% | Room for a rate rise at the next remortgage |
| New area, refurbished stock, uncertain rent | 20% or more | The rent assumption itself is the risk |
These bands are an indication, not a benchmark. A thin margin is not automatically a problem, as long as you know it is thin. It becomes one when the rent in your model is a hope rather than a comparable.
Ask a local letting agent to confirm the achievable rent before you build a calculation on it. A rent stress test then shows what happens to the margin when the rate moves. The ICR calculator works the ratio out from the figures you enter; the stressed rate and the cover floor are yours to supply.
Two mistakes that break this calculation
Using the pay rate instead of the stress rate. The rate on your offer is not the rate the test uses. On this loan the difference between 5.34% and a 6.5% stress rate moves the floor by nearly £200 a month. Ask your broker for the exact stress rate first.
Treating an ICR pass as a viable let. ICR ignores your service charge, insurance, agent fee, repairs and voids. A property can clear 145% cover and still run at a monthly loss. Run the cash flow separately, on the rate you actually pay.
Run your own numbers
Work the reverse sum above with the stressed rate and cover percentage your broker quotes, then enter your loan, rate, term and costs in BRIX Calc to see what the property earns at that rent. BRIX Calc applies no cover floor itself. Compare the result with the rent comparable properties on that street actually achieve, before you make an offer.
One project is free, and PRO removes the cap on how many you keep. It calculates projects: it gives no tax advice and fetches no market data. Start with the rental calculator.
Frequently asked questions
Does every lender use the same ICR requirement?
No. Requirements commonly sit between 125% and 145%, an indication rather than a benchmark, and the figure depends on your tax status, the fix length and whether you buy through a company. Stress rates vary too. Ask your broker for the exact test first, because twenty points moves the answer.
Can the minimum rent be higher than the market rent?
Yes, and finding that out early is the point of the calculation. If the market supports £850 and the test needs £907, the loan does not fit at that size. Your options are a larger deposit, a longer fix with a softer stress rate, or a different property altogether.
Does the minimum rent change on a capital repayment loan?
Nothing changes on a standard ICR test. The test uses notional interest at a stress rate, so the capital element never enters it. Cash flow is another matter: the payment is higher, so the rent that keeps the account positive sits well above the rent that passes.
Does this reverse calculation work on a development project?
Not in the same form. ICR and DSCR describe an income-producing hold, not a project that ends in a sale. On a development you reverse a different sum, from a target return on cost back to the minimum sale price. The principle is identical, the ratio is not.