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How lenders calculate affordability in 2026
18 June 2026 · 6 min read
Most UK lenders combine an income-based cap with an affordability stress test and take the lower of the two. Here is how the main three differ.
Two tests, lower wins
Almost every UK high-street lender applies both a loan-to-income (LTI) cap and an affordability stress test. The maximum loan they offer is the lower of the two figures.
The LTI cap is a multiple of gross annual income (typically 4.45× to 6.5× depending on income band). The stress test simulates the monthly repayment at a higher rate (typically 7.5%–8.5%) and asks whether your net income can absorb it after lifestyle, dependants and debts.
Where the lenders differ
NatWest is comparatively lenient on credit-card balances (weighted at around 50%) and rewards higher incomes with multiples up to 6.5×. Halifax weights CC balances at 75% and tops out around 5.5×. Barclays takes credit and maintenance commitments at close to full value and caps at around 5.0×.
Dependants and ongoing maintenance reduce capacity significantly — a single child can knock £16k–£24k off the LTI cap depending on lender.
Why our instant estimate is calibrated, not generic
Our calculator is reverse-engineered from 20 real Mortgage Brain Affordability Brain runs against NatWest, Halifax and Barclays. Results are typically within ±10% on clean cases. Your court-ready report uses the live lender models across 55+ lenders.
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- MCRs for solicitors: what to look for in a report
Not all Mortgage Capacity Reports are equal. Here are the markers of a report that will hold up in court.