London Buy-To-Let Stress Test: Average Flat Falls 113 Short

An average London flat falls about 113 pounds a month short of the rent a 75 per cent buy-to-let loan needs. Not because the rate is too high, and not because the buyer earns too little.

It fails a test that most people learn about after their application is declined. The London buy-to-let stress test works on rent, and London rent does not stretch far enough.

The test: 125 per cent cover at a 5.5 per cent rate

The Prudential Regulation Authority, the Bank of England body that supervises lenders, sets out buy-to-let underwriting standards in its supervisory statement SS13/16. Four paragraphs decide the outcome, and they read the same in the standing text and in the January 2026 update that takes effect on 1 January 2027.

Paragraph 2.3 sets the definition. The PRA expects firms to define the interest coverage ratio as "the ratio of the expected monthly rental income ... to the monthly interest payments which take into account likely future interest rate increases". Paragraph 2.7 records that "the current industry standard is to set the minimum ICR threshold at 125%". It adds that the PRA does not expect its proposals "to reduce minimum ICR thresholds" and that some factors "may lead to higher minimum ICR thresholds". So 125 per cent is the industry's ratio rather than the PRA's, and a floor of practice rather than a typical figure.

Paragraph 2.14 decides the outcome. It reads: "Even if ... the borrower's interest rate will be less than 5.5% during the first five years ..., the firm should assume a minimum borrower interest rate of 5.5%".

Note what that line does. The 5.5 per cent is not the rate you pay. It is the rate the lender must assume you might pay, so the test is unaffected by whether rates are rising or falling this quarter. It is a floor that applies whatever rate you are offered.

Put those together and the sum is short:

Annual rent must be at least the loan multiplied by 5.5 per cent, multiplied by 1.25. Turn it round and the same sum gives the ceiling: annual rent divided by 6.875 per cent.

Our London mortgage page sets out the product rules a lender will apply to a buyer living abroad, and our UK buying guide covers the rest of the transaction. This article does the sum those rules produce.

The cover test run on the average London flat

The Office for National Statistics puts the average house price in London at 569,000 pounds in July 2026, and the average private rent in London at 2,332 pounds a month in August 2026. Both figures come from the bulletin published on 16 September 2026.

Now fix an assumption, because the answer depends on it. This article runs the sum at a 75 per cent loan throughout. Treat that as a stated assumption rather than a rule, and scale the result at any other loan-to-value.

Take a 75 per cent loan on that price. The loan is 426,750 pounds. At the 5.5 per cent stress rate the assumed annual interest is 23,471 pounds. The cover ratio multiplies that by 1.25, so the property has to produce 29,339 pounds of rent a year, or 2,445 pounds a month.

The average London flat earns 2,332 pounds.

The shortfall is about 113 pounds a month. That is an average and not a quotation: change the price or the rent and the answer moves, which is why the sum has to be run on the specific flat. It is the reason an application that looks fine on income, deposit and credit history comes back with a smaller loan than the buyer expected, or with nothing at all.

Averages hide the range, so take a specific case. A 400,000 pound flat in an outer borough, bought with a 75 per cent loan, carries a 300,000 pound mortgage. At the stress rate that is 16,500 pounds of assumed annual interest, and the cover ratio lifts the rent required to 20,625 pounds a year, or 1,719 pounds a month.

That is a gross yield of 5.16 per cent, and that figure is the point: at a 75 per cent loan the test demands 5.16 per cent of the purchase price whatever the price is. On those ONS averages the London gross yield works out at 4.9 per cent, which is why the average flat fails. A cheaper flat does not pass because it is cheaper; it passes only if its rent clears the same 5.16 per cent. The test does not care about the size of the property or the location. It cares about the ratio between the two numbers, which is the figure to look for in our London listings.

Why England passes the same test

The ONS figures for England as a whole tell a different story at the same rate. The average English property cost 293,000 pounds in July 2026 and rented for 1,459 pounds a month in August.

• Average price. London: 569,000 pounds. England, including London: 293,000 pounds.
• Average monthly rent. London: 2,332 pounds. England, including London: 1,459 pounds.
• Gross yield. London: 4.9 per cent. England, including London: 6.0 per cent.
• Rent needed at 75 per cent borrowing. London: 2,445 pounds. England, including London: 1,259 pounds.
• Result. London: short by 113 pounds. England, including London: clears by 200 pounds.

Price and rent are ONS averages published on 16 September 2026. Gross yield, rent needed and result are SmartDecision calculations from those averages, using the 5.5 per cent stress rate, the 125 per cent cover ratio and a 75 per cent loan. The England column includes London.

London rent is the highest of the regional averages in the ONS series. It is also, on these averages, the market where rent covers the least of the purchase price, and that is the whole mechanism. The average London home costs roughly twice the English average, but the average London rent is not twice as high, it is about 60 per cent higher. Because price and rent did not grow in step, the gross yield falls, and the rent the test demands overtakes the rent the flat actually earns.

The ONS records an annual fall in London prices for eleven consecutive months, with the average price 19,000 pounds below its July 2025 peak. In the same bulletin London rents rose 3.5 per cent over the year and London prices fell 3.3 per cent. Both movements push the test in the borrower's favour, and neither has closed the gap yet.

What the cover test means for a non resident buyer

1. 1.The number to check first is the rent, not the rate. Divide the expected annual rent by 6.875 per cent. That is the largest loan the test will support.
2. 2.On these averages the rent supports about 71.5 per cent, not 75. That is the loan the average London rent actually covers. A product ceiling is a limit, not a promise that the rent will reach it.
3. 3.A smaller loan lowers the rent the test demands. Every point off the loan takes roughly 33 pounds a month off the rent the property has to earn.
4. 4.The test measures yield, not location. An outer borough flat at a lower price and a similar rent passes where a central one fails.
5. 5.The test looks at the flat, not at you. It measures the property's rent against the loan's assumed interest. Where you live, what currency you earn in and how much you earn sit in a separate part of the application.
6. 6.New build service charges are not in this sum. The test looks at rent against interest. The cash you actually keep is rent minus service charge, ground rent, management and void periods, and that is a separate calculation from this one.

The five-year fixed rate exception in paragraph 2.12

Paragraph 2.12 tells firms to consider likely future interest rates over at least five years. The duty falls away "unless the interest rate is fixed or capped for a period of five years or more from that time".

Read that carefully, because it is narrower than it is usually reported. The carve-out removes the obligation to look forward over five years. It says nothing about paragraph 2.14, which states the 5.5 per cent minimum without an express exception. SS13/16 does not say what a firm should assume in place of the 5.5 per cent minimum where a rate is fixed for five years or more, and firms set that individually. Where a firm tests the rent against the pay rate instead, the rent required falls and a flat can move from failing to passing without a penny more deposit. That is a question to put to the lender rather than an entitlement to claim.

A five-year fix has its own cost. A five-year fix locks the rate and the lender for the whole period, and the terms attached to it vary by firm. Paragraph 2.12 adds that the PRA "expects firms to consider the borrower's refinancing risk at the end of the fixed or capped rate period", so the question does not disappear, it moves to year five. It is one of the two variables in this sum a borrower can move, the other being the size of the loan.

Before you make an offer on a London flat

Run the sum on the specific flat before you agree a price: take the letting agent's rental estimate and divide it by 6.875 per cent. If it comes out short, the arithmetic only moves if the loan falls, the assumed rate falls or the rent rises.

The series to watch are the London rent and price indices in the ONS monthly bulletin. The gap closes only if rent growth outpaces price growth for long enough to lift the gross yield above 5.16 per cent. How a firm treats the 5.5 per cent minimum on a five-year fix is the other variable, and it is set firm by firm rather than published.

Our UK buying guide sets out the remaining cost lines, and our stock in the commuter towns carries the yields that clear this test on the same budget. SmartDecision Properties runs this calculation building by building before a client offers.

This article is general information. It is not mortgage, investment or tax advice, and it is not a credit quotation. Lending criteria vary between firms and the ratios described here are industry practice rather than a legal entitlement. Check your own position with a regulated mortgage adviser before you rely on any of these figures.