Working out how much mortgage you can afford is part maths and part risk management. Lenders are not asking what you could just about pay each month — they are asking what you can comfortably pay if interest rates rise, your income changes or unexpected costs arrive. This guide explains how UK affordability assessments actually work in 2026, how to estimate your borrowing range and what you can do to improve the number a lender is willing to give you.
Income multiples are only the starting point
Most UK lenders still talk in terms of income multiples — typically 4.5 times gross annual income for a single applicant and the same for joint income on two-applicant cases. Some lenders go to 5 or even 5.5 times income for higher earners, professionals such as doctors or teachers, or applicants with very large deposits. But the multiple is only the ceiling. The actual figure offered comes from a detailed affordability calculation.
Lenders take your gross income, deduct tax and national insurance, then subtract committed monthly outgoings such as credit card minimums, loan payments, car finance, childcare and ground rent. They apply a stress test to the mortgage payment to see whether you could still afford it if rates rose to a notional higher level. What is left after all of that is what they consider available for the mortgage.
How the stress test changes your number
Following changes to the Financial Policy Committee's recommendations, the rigid 3 percent stress test has been relaxed in recent years, but lenders still apply their own stressed rates, often product rate plus 1 to 3 percent. That means if a five-year fix is offered at 4.4 percent, the affordability sums may be done at something closer to 6 to 7 percent. That is why a mortgage broker can sometimes find you significantly more borrowing simply by moving to a longer fix where the stressed rate is lower.
A useful rule of thumb is that every additional £100 of monthly committed debt reduces the mortgage you can borrow by roughly £15,000 to £20,000. Clearing a small loan or credit card balance in the months before applying can therefore have a much bigger impact than people expect.
Deposit size, loan-to-value and pricing
The deposit you can put down sets the loan-to-value ratio, or LTV. Mortgage rates step down at 90, 85, 80, 75 and 60 percent LTV. A 5 percent deposit can get you onto the ladder using schemes such as the new mortgage guarantee scheme or shared ownership, but rates are noticeably higher than at 90 percent and significantly higher than at 75.
Saving a slightly larger deposit not only opens cheaper rate brackets but also reduces the amount you need to borrow, which makes the affordability test easier to pass. For many first-time buyers the difference between 8 and 10 percent deposits, or 13 and 15, is the most efficient lever they have.
Credit history and the things that quietly hurt
Lenders pull a full credit file and look at the last 6 years, with most weight on the last 12 to 24 months. Missed payments on mobile contracts, utility bills and buy-now-pay-later arrangements all count, even though many people forget about them. Frequent overdraft use and short-term high-cost credit such as payday loans are particular red flags.
Check your file with at least one of Experian, Equifax and TransUnion before you apply. Correct any errors in writing, register on the electoral roll at your current address and give the file 3 to 6 months to settle if you are about to apply for a mortgage.
What you can comfortably afford versus what you can borrow
Just because a lender will offer you a number does not mean you should take it. A more conservative test is to keep total housing costs — mortgage, council tax, building insurance, ground rent or service charge and average maintenance — below 35 percent of net household income. That gives you breathing room for rising rates, family changes and the inevitable unexpected costs of homeownership.
Run the numbers through an independent affordability calculator before talking to lenders, then use a whole-of-market broker to test which lenders fit your circumstances. The cheapest headline rate is rarely the cheapest deal once arrangement fees, valuation fees and incentives are taken into account.
Frequently asked questions
What income multiple do UK lenders use in 2026?
Most lenders use 4.5 times income, with some offering up to 5 or 5.5 for higher earners, professionals or large deposits.
Do I need a 10 percent deposit?
No. 5 percent deposit mortgages exist through the mortgage guarantee scheme and selected lenders, but rates and acceptance criteria are tighter.
Will buy-now-pay-later affect my mortgage?
Yes. BNPL agreements typically appear on credit files and count as committed monthly outgoings, reducing borrowing capacity.