UK mortgage affordability rules: FCA checks, 4.5x limit

Two different sets of rules

People often mix up two things.

• Affordability rules (FCA). They apply to every regulated mortgage, lender by lender and borrower by borrower. They decide whether you can be lent a given amount.
• The loan-to-income flow limit (Bank of England). It is a financial-stability tool for the whole market. It limits how many loans a lender makes at high multiples of income. It is not a rule that stops you from borrowing more than 4.5 times your income.

The FCA’s rules are UK-wide. Mortgage regulation is not devolved, so the rules below are the same in England, Scotland, Wales and Northern Ireland.

What the FCA requires of a lender

The Mortgages and Home Finance: Conduct of Business sourcebook (MCOB) sets the standard in chapter 11.6.

Income. The lender must obtain evidence of the income you declare for the application and must not accept self-certification (MCOB 11.6.8R). It may not rely on a general declaration of affordability from you (MCOB 11.6.6R). Affordability is worked out on income after tax and National Insurance.

Spending. A lender may generally rely on the information you give about spending, unless it has reason to doubt it, but it must take reasonable steps to find your actual outstanding commitments, such as loans and cards (MCOB 11.6.12R). Basic essential costs and quality-of-living costs can use your actual spending or modelled data, and modelled data must reflect your household and use realistic assumptions.

Future changes. Known changes, such as a planned drop in income, must be taken into account (MCOB 11.6.14R).

Property value. The assessment must not rely on the equity in the property (MCOB 11.6.5R). A lender cannot approve a loan because the home might rise in value.

Retirement. If the mortgage term runs past your expected retirement, the lender should take a prudent approach to your income after that date, and the closer you are to retiring, the firmer the evidence should be (MCOB 11.6.15G).

The interest-rate stress

A lender must consider likely future interest rates over a minimum of five years, unless your rate is fixed for that period or for the whole term if shorter (MCOB 11.6.18R). It must assume rates will rise by at least 1% even if market expectations are flat or falling. The guidance gives the forward sterling rate published on the Bank of England website as an example of market expectations.

In practice, this is why a lender may offer less than a calculator based on today’s rate suggests. Each lender builds its own model on these minimum standards, so offers differ between lenders.

The Bank of England 4.5x limit

The Bank of England’s Financial Policy Committee recommends that the aggregate flow of new mortgages at a loan-to-income ratio of 4.5 or more does not exceed 15% of all new mortgages. Policy statement PS19/26, published on 14 October 2026 by the Bank’s Prudential Regulation Authority and the FCA, says:

• the firm-specific 15% cap is removed, and lenders can set their own strategies for high loan-to-income lending;
• the 15% aggregate remains the control: lenders may exceed 15% individually while the market total stays within a level consistent with the recommended limit;
• a “high” loan is one where the credit is, or exceeds, 4.5 times the individual’s income, or joint income for joint borrowers;
• the 4.5 threshold and the 15% level are not recalibrated in this statement;
• firms are exempt if, across two consecutive four-quarter periods, they provided credit under £150 million or entered fewer than 300 regulated contracts;
• the PRA rules take effect on 28 October 2026.

Until that date, treat the change as coming, not in force. For first-time buyers, the ONS reports an average loan-to-income ratio of 3.6 in 2025, with 3.7 in England, 3.4 in Wales and 3.1 in both Scotland and Northern Ireland.

What you can do

• Gather payslips, bank statements and details of every debt before you apply: the lender must evidence your income.
• Reduce monthly commitments before applying, since they enter the spending assessment.
• Compare what different lenders would offer: the same income can give different figures.
• Ask a lender for a mortgage in principle for a first indication, then confirm with a lender or adviser. Our guide to the deposit and loan-to-value covers the other side of the lending decision.

Which professional to consult

A regulated mortgage adviser or broker can compare lenders’ criteria for your income type, such as self-employment or bonuses, and explain why one lender offers more than another. See the mortgage adviser page. Check any firm yourself on the FCA register before you give personal details.