Mortgage Affordability: How Lenders Decide

What Is an Affordability Assessment?

An affordability assessment is the process lenders use to determine whether you can afford a mortgage. It was made a formal requirement following the Mortgage Market Review, which introduced stricter rules to ensure responsible lending across the UK mortgage market.

The assessment goes far beyond simply looking at your income. Lenders examine your entire financial picture, including your regular expenditure, existing debts, and future financial commitments. The aim is to ensure that you can afford your mortgage payments not just at the initial rate but also if interest rates were to rise.

Every lender has its own affordability model, which is why two lenders can look at the same application and reach different conclusions about how much they are willing to lend. This is one of the key reasons why using a mortgage broker can be so valuable.

What Lenders Look At

During an affordability assessment, lenders typically examine the following:

• Gross and net income – your salary before and after tax, including any regular bonuses, overtime, or commission. Lenders vary in how much of variable income they will include.
• Other income sources – rental income, pension payments, child maintenance, benefits, or investment income may be considered, though different lenders treat these differently.
• Regular outgoings – council tax, utility bills, insurance, childcare, school fees, and other committed expenses.
• Existing debt payments – minimum credit card payments, loan repayments, hire purchase agreements, and student loan repayments.
• Living costs – lenders use either your declared expenses or statistical models (like the ONS data) to estimate your cost of living.
• Future changes – some lenders ask about planned changes such as starting a family, reducing working hours, or approaching retirement.

The lender then calculates whether your income minus your expenses leaves enough room to cover the mortgage payment, with a buffer for potential rate increases.

Stress Testing Your Mortgage

One of the most important parts of the affordability assessment is the stress test. Lenders need to check that you could still afford your payments if interest rates were to rise. They do this by calculating your payments at a higher rate than the one you are applying for.

The stress test rate varies between lenders but is typically two to three percentage points above the deal rate, or the lender's SVR plus a margin. For example, if you are applying for a deal at four per cent, the lender might check that you could afford payments at six or seven per cent.

This stress testing explains why some borrowers are surprised to be offered less than they expected. Even if you can comfortably afford the payments at the current rate, the lender needs to be satisfied that you could manage if rates increased significantly.

How to Improve Your Affordability

If you are concerned about passing an affordability assessment, there are practical steps you can take:

• Reduce your debts – paying off or reducing credit card balances, loans, and other debts directly improves your affordability profile.
• Cut unnecessary spending – lenders review your bank statements, so reducing discretionary spending in the months before you apply can help.
• Close unused credit accounts – some lenders factor in available credit, not just used credit. Closing unused accounts can improve your position.
• Extend the mortgage term – a longer term reduces the monthly payment, which may help you pass the affordability test. However, you will pay more interest overall.
• Consider a joint application – if you have a partner or family member who could be added to the mortgage, their income may boost your borrowing power.

Remember that different lenders have different affordability models. A broker can help you find the lender whose criteria best suit your financial circumstances.