More than three quarters of UK mortgage brokers (76%) say the mortgage application process is faster than it was two years ago, yet complex cases are still failing at key points in the journey.

A survey by Nottingham Building Society found that automated income or credit checks are now the single most common point at which complex income cases fail or stall, cited by 17% of brokers.

A further 16% say cases break down at the initial affordability assessment or decision-in-principle stage, showing that friction remains high at the point where lenders make early calls on what counts as acceptable income, expenditure, or risk.

The scale of the issue is compounded when considering the size of what would be perceived as the ‘complex income’ market.

A 2025 UK Finance Survey found that around 28% of mortgage applicants now report income from more than one source. Sage research in 2024 also cited that 47% of the UK population have a second income stream.

Delays are proving just as damaging further down the line, as 16% of brokers say time delays are causing cases to fall through.

Another 14% cite evidence and documentation requirements as a key source of friction.

Brokers say those most disadvantaged by current mainstream affordability assessments include people returning from career breaks (32%), borrowers with multiple income streams such as PAYE and freelance work (31%) and applicants with irregular or seasonal income (29%).

Brokers are also clear about where lenders should focus next. A third (33%) say better handling of complex or non-standard cases would have the biggest positive impact on their ability to place business, which suggests the real gap is no longer basic processing speed alone, but how the system responds when an application needs flexibility.

Around a third also call for clearer tracking of case progress (33%), better integration between broker systems and lenders (32%) and faster decision making (32%), pointing to a market that still needs stronger visibility, coordination and consistency if it is to support more complex borrowers well.

Nottingham Building Society chief lending officer Aaron Shinwell said: “These findings show that the market is making progress, but others are still being left behind.

“Straightforward cases are moving more quickly, which is welcome, yet brokers are still seeing the same pressure points emerge when a borrower’s circumstances need a little more interpretation, whether that is blended income, a career break, variable earnings or a case that simply needs more manual review.

“The next step is targeted improvement at the stages where cases most often come under strain. That means making automated checks more responsive to real-life income patterns, improving transparency as cases move through the system and reducing delays where extra documentation or judgement is needed.”