How mortgage lenders work out what you can borrow

By Andrew Gillespie · Published 20 October 2026

Income multiples, affordability checks, stress tests, deposits and credit history: how UK lenders decide how much to lend, and what you can do to improve your chances.

Online calculators often give a single "you can borrow" figure based on your salary. Real lending decisions are more detailed. UK lenders must check that a mortgage is affordable for you now and could stay affordable if things change. This guide explains the main factors and how to put yourself in the best position.

Income multiples: the starting point

Many lenders start with a multiple of your income, commonly up to about 4 to 4.5 times gross annual income for most applicants, sometimes more for higher earners or certain professions. For joint applications, both incomes are usually combined. The Bank of England also limits how much lending at high multiples (4.5 times or above) lenders can do overall, so these loans are rationed.

The multiple is a ceiling, not a promise. The detailed affordability check often produces a lower figure.

Affordability: income vs outgoings

Under the Financial Conduct Authority's responsible lending rules, a lender must assess whether you can afford the mortgage, using evidence of your income and a realistic view of your spending. Expect to provide:

recent payslips and a P60, or two or more years of accounts or tax calculations if self-employed;
bank statements, which lenders use to check income and regular spending;
details of credit commitments: loans, car finance, credit card balances and buy-now-pay-later;
regular costs such as childcare, maintenance payments and travel to work.

High monthly commitments reduce how much you can borrow, sometimes considerably. Clearing a small loan or car finance deal before applying can make a difference.

The stress test

Lenders must consider the effect of interest rates rising over the first five years of the mortgage, and check you could still afford the payments. Choosing a fix of five years or more can, with some lenders, reduce the impact of this test.

Deposit and loan to value

Your deposit determines the loan to value (LTV). A bigger deposit usually means a lower rate and a wider choice of lenders. Many lenders offer mortgages up to 90% or 95% LTV, but the best rates are usually at 60% or 75% LTV and below. Lenders will want to know where the deposit comes from; a gift from family usually needs a letter confirming it is a gift, not a loan.

Your credit history

Lenders will check your credit file with one or more credit reference agencies. Missed payments, defaults or a county court judgment in recent years can limit your options. Make sure you are on the electoral roll, check all three files for errors, and avoid new credit applications in the months before you apply.

Step by step: improve your chances

Check your credit files and fix mistakes.
Reduce debts and avoid new credit, including buy-now-pay-later.
Look at your bank statements as a lender would, and cut non-essential spending in the months before you apply.
Build your deposit. Moving from one LTV band to the next can lower your rate.
Get an agreement in principle, which gives a guide figure. Some use a soft search.
Consider a broker, who can match your circumstances to suitable lenders.

Borrowing less than the maximum

The most a lender will offer is not necessarily what you should borrow. Leave room in your budget for rate changes when your deal ends, maintenance, insurance, service charges and life events. A longer term lowers monthly payments but increases the total interest.

Frequently asked questions

Do bonuses and overtime count?

Often partly, if they are regular and can be evidenced. Policies vary by lender.

Does a student loan affect how much I can borrow?

It is not on your credit file, but lenders count the monthly repayment as an outgoing, which reduces affordability.

Sources and further reading

Facts checked on 20 October 2026. Spotted an error? Tell us and we will correct it.