Mortgage affordability under MCOB 11.6 is a lender control, not simply a calculation performed at the point of application. A mortgage lender needs to be able to demonstrate that the customer can pay the sums due, explain the evidence and assumptions supporting that conclusion and maintain a framework that remains appropriate as products, customer populations and economic conditions change.
The distinction matters in 2026 because the FCA is simultaneously simplifying parts of the mortgage rulebook and reinforcing responsible lending as a core principle. Its Mortgage Regulatory Priorities expect lenders to monitor and oversee affordability assessments so that they continue to deliver good outcomes, including where firms broaden access. The FCA's second charge review also found examples of expenditure assumptions that did not appear realistic for the customers being served.
This article therefore focuses narrowly on the control environment behind MCOB 11.6. Regulatory Counsel already has separate guidance covering the broader relationship between mortgage affordability, vulnerability and arrears. The purpose here is to examine how lenders should design, evidence, validate and challenge the affordability assessment itself.
Start with the current scope of MCOB 11.6
MCOB 11 applies to mortgage lenders and certain home purchase plan providers in accordance with its application provisions. MCOB 11.6 contains the principal affordability rules for regulated mortgage contracts and home purchase plans, subject to the detailed scope, exceptions and modifications in the current Handbook.
The core rule is that, except where a current exception applies, the lender must assess whether the customer will be able to pay the sums due before entering into or agreeing to vary the contract and must not proceed unless it can demonstrate that the mortgage is affordable. This is different from a general sense that the customer appears financially comfortable. The decision needs an evidential basis.
The Handbook contains exceptions and modified approaches for particular circumstances, and the rules were amended again on 26 June 2026. Firms should therefore avoid relying on a historic summary of when a full affordability assessment is required. Product and change teams should use the current rule set when designing customer journeys, including replacement mortgages, variations and forbearance-related changes.
The control should make scope visible. Staff and systems need to know when the standard assessment applies, when a permitted exception is being used and what evidence is required to support that route.
Income evidence should reflect sustainability, not only the current figure
Affordability depends on income that is sufficiently reliable for the period relevant to the mortgage. The exact evidence can differ by customer, but the lender's methodology should explain how different income types are treated and what degree of verification or haircut is applied.
A salaried customer with stable earnings presents a different evidential question from a self-employed applicant, contractor, customer relying on variable bonus income or borrower expecting to retire during the mortgage term. The model should not simply convert every income source into an annual figure without considering sustainability.
Known or reasonably foreseeable changes matter. If the mortgage extends into retirement, or the lender knows that a material income source is temporary, the assessment should address what happens when that income changes. The affordability conclusion should not depend on an assumption that contradicts information already available to the firm.
Automated income verification can improve efficiency, but it does not remove governance responsibility. Management should understand the data source, failure modes and circumstances in which manual review is required. If an automated system cannot interpret a particular income structure reliably, forcing the case through the standard model can create false precision.
Expenditure assumptions need to match the customers the lender actually serves
The FCA's 2026 second charge work placed particular emphasis on expenditure assessments. It found that some assumptions did not appear realistic for the customer population and that certain types of expenditure were not always adequately considered.
A lender can use statistical data and models where permitted by the rules, but the methodology should remain appropriate for the people actually borrowing. A generic benchmark can become weak if the firm's customers have materially different household profiles, debt burdens or essential costs.
The firm should therefore know where its expenditure data comes from, how often it is reviewed and what evidence shows that it remains reasonable. Validation should compare assumptions with actual application or customer data where possible rather than simply confirming that the external dataset is still published.
The assessment should also have a route for information that falls outside the model. If the customer discloses a significant committed or essential cost that is not reflected adequately in the standard assumption, the process should capture it rather than allow the statistical model to override known facts.
A pattern of manual additions or repeated underestimation in one customer segment can indicate that the base model needs recalibration.
Stress testing should be governed as a model, not a fixed number
MCOB requires lenders to take account of the impact of likely future interest rate increases in relevant cases. The FCA has separately published material explaining the flexibility available within the interest rate stress test rule and the need for lenders to consider the rule in the context of their own products.
The stress assumption should therefore have a documented rationale. Management should know which rates, market expectations or product characteristics influence the test, how the approach differs across fixed, variable and reversion structures and what governance applies when assumptions change.
A stress rate can become stale even where it still produces technically plausible numbers. The lender should review whether the assumption remains meaningful against current product pricing and the likely payment path faced by customers.
Alternative approaches can be legitimate where the rules permit them, but the firm should be able to demonstrate why the method still tests affordability appropriately. The more model discretion a lender uses, the more important model governance and validation become.
The result should be understandable to senior management. A board does not need to reproduce the calculation, but it should know the material assumptions that drive approval rates and where changes in those assumptions would alter customer outcomes.
Automated affordability models need controls over data, logic and change
Many lenders use automated affordability engines that combine customer information, external data and policy rules. Automation can improve consistency, but it also concentrates risk because one model error can affect a large customer population.
The control framework should identify who owns the model, who approves changes, what testing occurs before deployment and how material defects are detected after launch. Changes to expenditure assumptions, stress rates, treatment of income or policy thresholds should be subject to version control and documented approval.
Data quality is equally important. A sophisticated model cannot compensate for inaccurate income, incomplete commitments or information lost between intermediary and lender. Input validation should therefore be part of model governance rather than treated as a separate operational issue.
Management should also understand where the model uses proxies or statistical assumptions rather than customer-specific data. Those choices may be appropriate, but their limitations should be known and monitored.
Post-implementation monitoring can compare expected and actual outcomes. Early payment difficulties, high levels of manual intervention or materially different performance in one segment can indicate that the affordability framework needs review even where the original model validation passed.
Overrides and exceptions should be visible and challenged
A lender may allow underwriters to override automated outputs or make judgement-based decisions in circumstances where policy permits it. That flexibility can improve outcomes where the standard model does not capture an individual case well, but it creates a separate control risk.
The firm should define who can override, the types of decision that can be changed and what evidence must be recorded. A free-text box saying "manual approval" is not sufficient where the override changes a material affordability conclusion.
Override MI should be reviewed for patterns. If one team or product has a materially higher override rate, management should understand whether this reflects customer complexity, model weakness or commercial pressure.
The direction of the override matters too. Repeated decisions that make the affordability test more permissive deserve particular scrutiny because they can indicate that risk appetite is being applied outside the model. More conservative overrides can also reveal that the base model is producing approvals that experienced underwriters do not trust.
A strong governance process therefore uses override data as model feedback rather than treating each exception as an isolated case.
Second charge lending needs the full secured debt picture
Second charge lenders need to assess affordability in the context of the customer's existing first charge and other relevant commitments. The new loan does not replace the existing mortgage, so the payment burden needs to reflect the combined position.
The FCA's second charge findings reinforce the importance of realistic expenditure and complete information. Where the intermediary has collected details of debts, payment difficulties or other customer circumstances, the lender should receive the information needed for its own assessment.
This makes distribution controls part of affordability governance. The lender should know which fields are mandatory, how inconsistencies are handled and whether information is lost when broker systems transfer data into the lender's platform.
Second charge portfolios can also provide useful model-performance evidence because customers may have lower financial resilience and higher debt burdens. Early arrears, forbearance and complaint outcomes should be considered when validating whether affordability assumptions remain appropriate.
Consumer Duty changes how management should review affordability outcomes
The Consumer Duty does not replace MCOB 11.6, but it changes the way firms should think about evidence. A lender should understand whether the affordability framework is delivering good outcomes for the customers it serves and whether particular segments experience materially poorer results.
Approval rates alone do not answer that question. A model that approves more customers can support access to credit, but management should also examine subsequent payment performance, financial difficulty, complaints and other evidence of whether the lending decision was sustainable.
This is particularly relevant as the FCA seeks to rebalance risk and improve mortgage access. Firms may use regulatory flexibility to serve customers previously excluded by conservative criteria, but the FCA's Mortgage Regulatory Priorities make clear that firms remain responsible for the outcomes they deliver.
Outcome analysis should therefore feed model governance. If one route or customer group shows materially higher early arrears or support needs, the lender should investigate whether the affordability assumptions, product design or customer support framework needs to change.
The June 2026 Mortgage Rule Review proposals are not current law
The FCA consulted in June 2026 on further responsible lending changes intended to support first-time buyers and underserved consumers. The consultation closed on 28 July 2026.
Those proposals are strategically important, particularly for firms considering variable income, later-life lending and customers with past credit difficulties. They should not, however, be implemented as though they are already the current MCOB rules unless and until final rules take effect.
Compliance and product teams should maintain a clear change log separating current requirements from proposed future changes. This reduces the risk of a firm inadvertently weakening a live control because a consultation suggested that greater flexibility may be introduced later.
When final rules arrive, the lender should update scope logic, models, procedures, training and monitoring as a controlled change rather than simply amend the policy wording.
What should the board see?
Senior management should understand the assumptions that drive the affordability framework and the outcomes produced by it. Useful information can include model approval and decline rates, overrides, changes to assumptions, early arrears, customer segments with weaker performance, second charge outcomes and material data-quality issues.
The board should also understand when the model was last validated and what evidence supported that conclusion. A statement that the model is "within policy" is less useful than a clear explanation of whether the assumptions remain appropriate for the firm's current customers and products.
Affordability governance is strongest where the firm can connect policy, model logic, actual customer data and subsequent performance. That is the evidence that allows management to demonstrate responsible lending rather than simply point to a calculation completed at application.
How Regulatory Counsel can support
Regulatory Counsel supports mortgage lenders with MCOB 11.6 affordability framework reviews, model governance, stress testing assumptions, expenditure methodology, override controls, second charge lending and Consumer Duty outcome analysis.
We can review a specific affordability model or the wider responsible lending control framework.
Speak to Regulatory Counsel to discuss a mortgage affordability review.
Frequently Asked Questions
Yes. The formal affordability assessment under MCOB 11.6 applies principally to mortgage lenders and relevant home purchase plan providers according to the chapter's scope. Mortgage advisers have separate suitability obligations.
The MCOB framework permits the use of appropriate statistical data in relevant circumstances, but firms need a methodology that remains realistic for the customer population and takes account of known customer information.
The current MCOB framework contains requirements for lenders to consider likely future interest rate increases in relevant cases, subject to the detailed rules and exceptions. Firms should use the current Handbook rather than a historic summary.
No. The June 2026 consultation closed in July 2026. Firms should distinguish those proposals from current rules unless and until final changes take effect.
Yes. A review can cover rule mapping, data inputs, expenditure assumptions, stress testing, overrides, governance, validation and customer outcome evidence.