How does the mortgage affordability income multiplier work?

Full answer

The "income multiple" is a simple shorthand many buyers use to estimate what they might be able to borrow, but modern UK mortgage lending relies on a much more detailed affordability assessment underneath that headline figure. **The traditional multiple as a starting point** Most mainstream lenders will quote a standard maximum multiple of roughly 4 to 4.5 times a single applicant's income, or a similar multiple applied to combined joint income for couples, sometimes higher (up to 5 or 5.5 times) for certain professions (such as some qualified professionals) or higher-income applicants who meet specific lender criteria. This gives a rough, easy first estimate of maximum borrowing. **Why the actual maximum can differ from the simple multiple** Since mortgage market reforms following the financial crisis, lenders are required to carry out a full affordability assessment that looks well beyond a simple income multiple -- examining your actual monthly outgoings (existing debts, credit card balances, car finance, childcare costs, general living costs), number of dependants, and results of the interest rate stress test. Two applicants with identical income can be offered very different maximum loans if one has significant existing debt or several dependants and the other does not, even though the simple "multiple of income" formula would suggest they qualify for the same amount. **How dependants and existing debt reduce the effective multiple** Each dependant (typically children) reduces the amount of income a lender assumes is available for mortgage repayments, since some income must cover the cost of raising them -- lenders build assumed living costs per dependant into their calculations. Similarly, existing debt repayments (car finance, credit cards, personal loans, and in some cases even student loan repayments) reduce disposable income available for a mortgage, lowering the effective borrowing capacity below what the simple headline multiple would suggest. **How bonus, overtime and self-employed income are treated** Variable income such as bonuses, overtime, or self-employed profits is often only partially counted towards the affordability assessment (commonly at a percentage such as 50% of the variable element, or an average over two to three years for self-employed income), meaning someone with a lower base salary but a large bonus may not get full credit for the bonus income in the multiplier calculation, again pulling the effective borrowing below the theoretical headline multiple. **Worked example** Two single applicants both earn £50,000 a year, suggesting a theoretical maximum loan of around £200,000-£225,000 at a 4-4.5x multiple. Applicant A has no debts and no dependants, and is offered close to the full £225,000. Applicant B has two dependent children and £400 a month of car finance and credit card repayments, and after the lender's full affordability assessment, is offered only around £170,000 -- notably below the simple 4x multiple, because their real disposable income after outgoings and dependant costs is significantly lower. **Practical tip** Use a simple income multiple as only a rough starting estimate, and get a proper Decision in Principle or speak to a mortgage broker for a realistic figure based on your actual income, debts and family circumstances -- relying purely on the "4.5 times salary" rule of thumb can lead to significant disappointment if your outgoings are higher than average.

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More answers

• What is a mortgage stress test and why do lenders use it?
• What is a Decision in Principle (DIP) and how long is it valid?