Income multiples, affordability tests, and the factors that determine your maximum mortgage, explained clearly by specialist brokers with whole-of-market access.
The most widely quoted rule in mortgage lending is the income multiple, the relationship between your salary and the amount you can borrow. In practice, most high-street lenders will offer between 4 and 4.5 times your annual income. Some specialist lenders will extend to 5 or even 5.5 times income for the right applicant.
For a joint mortgage, lenders use combined household income. Two applicants each earning £40,000 would have a combined income of £80,000, giving a borrowing range of £320,000 to £360,000 at standard multiples.
| Annual Income (sole) | 4x Multiple | 4.5x Multiple | 5x Multiple |
|---|---|---|---|
| £30,000 | £120,000 | £135,000 | £150,000 |
| £40,000 | £160,000 | £180,000 | £200,000 |
| £50,000 | £200,000 | £225,000 | £250,000 |
| £60,000 | £240,000 | £270,000 | £300,000 |
| £80,000 | £320,000 | £360,000 | £400,000 |
| £100,000 | £400,000 | £450,000 | £500,000 |
These are maximum borrowing figures, not automatic entitlements. Your actual offer will depend on your credit score, outgoings, deposit size, and how the lender assesses your income. Use our affordability calculator for a quick estimate, then speak to an adviser for a precise figure.
Income multiples are a starting point, but lenders don't just divide your salary by four and hand you a mortgage offer. Modern affordability assessments are more detailed, and more nuanced.
Every lender runs an affordability calculation that models your current income against your outgoings, then tests whether you could still afford the mortgage if interest rates were to rise. This is called a stress test.
Lenders don't assess affordability at the rate you'll actually pay. They typically stress-test your payments at a notional rate of 7–8%, regardless of the current rate on the product. This means your maximum borrowing is often lower than the income multiple alone suggests.
For example: if you're borrowing at a 4.5% fixed rate, the lender might calculate your payments as if the rate were 7.5%. If you couldn't afford the payment at 7.5% based on your income and outgoings, the application would fail, even if you can comfortably afford the actual monthly payment.
Several factors can push your borrowing limit below the income multiple headline figures. Understanding these is key to knowing what to expect, and what to address before you apply.
Not all income is treated equally. Lenders are required to verify and stress-test every income source, and some apply haircuts or restrictions to certain income types.
The most straightforward income type. Lenders will use your basic salary in full. Overtime, bonuses, and commission are typically accepted at 50–100% depending on how regular and evidenced they are. Some lenders average 2–3 years of variable income to reach a usable figure.
Self-employed applicants need to demonstrate income over a 2–3 year period, typically using SA302 tax calculations and tax year overviews. Company directors are assessed on salary plus dividends or, in some cases, net profit. Specialist lenders offer more flexible approaches for contractors assessed on day rate rather than accounts.
For residential mortgages, some lenders will include rental income from investment properties in their affordability calculation. This can significantly increase the maximum borrowing for portfolio landlords. The treatment varies significantly between lenders, this is where a whole-of-market broker can identify the best approach.
Benefits, pension income, maintenance payments, investment income, and rental income are all treated differently by different lenders. Some lenders are much more generous than others in what they will include. A specialist broker will know which lenders to target based on your specific income mix.
If your current maximum borrowing isn't sufficient for the property you want, there are practical steps worth taking before you apply:
1. Clear or reduce existing debt commitments. Even small monthly payments have an outsized impact on affordability calculations. A £200/month loan can reduce your maximum mortgage by £20,000–£30,000. Paying it off before applying is usually worth it if the numbers stack up.
2. Increase your deposit. More equity means lower LTV, which opens the full lender market and the most generous income multiples. It also reduces the loan required, which may bring a previously out-of-reach property into range.
3. Extend the term. A 35 or 25-year term reduces monthly payments and can improve the stress test outcome. You can always overpay or remortgage to a shorter term when your income grows.
4. Use the right lender. Affordability criteria vary significantly between lenders. The same application can result in very different maximum loan amounts depending on which lender you approach. A whole-of-market broker will identify the most generous lender for your specific profile.
High-street lenders offer their own products, applying their own affordability model. A whole-of-market broker like The Mortgage Consultancy can identify the lender whose criteria best fits your circumstances, often unlocking meaningfully more than a direct application would achieve.
The definitive way to find out how much you can borrow is to obtain an Agreement in Principle (AIP), also called a Decision in Principle or Mortgage in Principle. This is a conditional statement from a lender confirming how much they would be prepared to lend, subject to a full application and valuation.
An AIP requires a credit check (usually a soft search, which does not affect your credit score) and basic income and commitment details. Most lenders issue an AIP within minutes of application.
Estate agents will typically ask to see an AIP before accepting an offer, it demonstrates that you are a serious buyer with finance in place. Your mortgage adviser can obtain an AIP from multiple lenders as part of the research process, without leaving any trace on your credit file.
Use our affordability calculator for an instant estimate, then speak to an adviser who will identify the lender with the best criteria for your specific situation.