Mortgage Affordability

How lenders assess affordability

The question "how much can I borrow?" has two answers: the income multiple (a quick rule of thumb) and the affordability assessment (what a lender will actually offer after looking at your full financial picture). Both matter — but they often produce very different numbers.

Income multiples: a starting point

The traditional rule of thumb is that lenders will lend up to 4–4.5 times your annual income. This gives a useful ballpark figure and is still widely used in the industry. For joint applications, the combined income is used. A household earning £45,000 + £30,000 = £75,000 combined could expect to borrow up to £337,500 at 4.5×.

Income multiples are not fixed by law — they're policies set by individual lenders. Some lenders consistently offer 5× to certain borrowers (typically higher earners or key workers). Going above 4.5× usually requires specialist lenders or specific criteria to be met.

What lenders actually look at

Since the Mortgage Market Review (MMR) in 2014, lenders are required to conduct a full affordability assessment, not just apply an income multiple. This means:

• Income: employed, self-employed, bonus, rental, benefits — how reliable and provable it is matters.
• Existing commitments: monthly debt payments reduce the amount you can borrow. A £400/month car finance payment can cut your mortgage offer by £40,000–£60,000.
• Outgoings: regular spending on bills, childcare, subscriptions. Bank statements are typically reviewed.
• Credit score and history: missed payments, defaults, CCJs, and high credit utilisation all reduce what you'll be offered.
• Employment status: self-employed borrowers typically need 2–3 years of accounts. Those on probation may be declined by some lenders.
• Age: the mortgage must complete before the lender's maximum age (typically 70–75) unless a retirement interest-only product is used.

Stress testing

Lenders are required to stress test your affordability — checking that you could still afford the mortgage if interest rates rise. The standard stress test adds approximately 3% to the initial rate. If you're applying at 5%, the lender models whether you could afford payments at 8%.

This stress test is a regulatory requirement introduced by the Bank of England's Financial Policy Committee. It's one of the main reasons some applicants are offered less than the income multiple suggests — their finances pass at 5% but fail at 8%.

Loan to value (LTV) and its impact

Your LTV is the loan amount divided by the property value. A £270,000 mortgage on a £300,000 property is 90% LTV. Lower LTVs typically attract better interest rates — the difference between 60% and 90% LTV can be 0.5–1.5% per year, which translates to a significant difference in monthly payments.

• 95% LTV: available but expensive. Rates are highest; some lenders exclude certain property types.
• 90% LTV: more lenders available; better rates than 95%.
• 85% LTV: significant improvement in available rates.
• 75% LTV: most competitive rates begin to become available.
• 60% LTV: typically the best rates in the market.

Mortgage term

The standard mortgage term used to be 25 years. Many borrowers are now taking 30 or even 35-year terms to reduce monthly payments and improve affordability. A longer term reduces the monthly payment but significantly increases the total interest paid. This calculator uses 25 years for comparability, but your actual term may differ.

Getting an Agreement in Principle

An Agreement in Principle (AIP) — also called a Decision in Principle or Mortgage in Principle — is a conditional indication from a lender that they would be willing to lend a specific amount. Most lenders offer soft-search AIPs that don't leave a mark on your credit file. Having an AIP is almost essential before making an offer, as many estate agents won't take offers seriously without one.

An AIP is not a mortgage offer — the full application and underwriting still needs to happen. But it gives you and the seller confidence that you're a serious, fundable buyer.