What affects mortgage affordability?

UK mortgage affordability is a mix of income multiples and a forward-looking stress test. Both matter, and the second is where most people are caught short.

Income multiples

Most lenders cap borrowing at 4× to 4.75× combined income. A growing number lend up to 5.5× for higher earners and certain professions (doctors, solicitors, accountants, engineers).

Committed outgoings

Lenders deduct from your income: monthly loan payments, credit card minimums, car finance, childcare, school fees, ongoing maintenance payments. Even a manageable £400/month commitment can shave £25k–£40k off your borrowing.

Dependants

Each dependant (typically children) reduces affordability via a notional cost — usually £300–£500/month per child for most lenders.

Stress tests

Lenders model your payments at a higher rate — often 1–3% above the current SVR or product rate. This is the single biggest reason borrowing capacity has dropped since 2022.

How to maximise borrowing

• Clear small loans and credit cards.
• Stop using overdrafts in the 3 months before applying.
• Avoid Buy Now Pay Later — flagged as commitments.
• Use a broker who knows which lender favours your profile.
• Consider a longer term — lowers the stress-test payment.