Navigating Complex Income in a Changing UK Workforce

The idea of a single, predictable salary underpinning a mortgage application is becoming less representative of how people actually earn in the UK.

Across sectors and age groups, more workers are building careers made up of multiple income streams: a core role supplemented by a second job, regular overtime, commission, bonuses or a car allowance. Others are employed on fixed-term contracts or zero-hours arrangements but have strong, consistent earnings over time. What was once considered “complex” income is, for many households, simply normal income.

The data supports this shift. According to the Office for National Statistics (ONS), around 1.3 million people in the UK were holding a second job during 2023–2024, accounting for roughly 4% of those in employment. Meanwhile, HM Revenue & Customs reports that more than 11.5 million people submitted Self-Assessment tax returns for 2023–24, reflecting the scale of additional or non-PAYE income across the country.

This doesn’t just represent gig economy workers or freelancers. It includes teachers tutoring in the evenings, healthcare professionals taking additional shifts, employed professionals receiving structured bonuses, and employees whose remuneration packages include regular commission or allowances. In many cases, these additional income streams are not occasional windfalls; they form a meaningful and sustainable part of household earnings.

For the mortgage market, this evolution presents both a challenge and an opportunity.

Traditionally, underwriting models were built around fixed basic salary. Variable income was often discounted heavily or ignored altogether, partly as a risk control measure and partly because it was less common. Today, however, failing to recognise stable supplementary income can distort affordability assessments and exclude borrowers whose overall financial position is sound.

The key distinction is not whether income is variable, but whether it is sustainable.

A borrower receiving annual bonuses for five consecutive years presents a very different risk profile from someone who received a single, exceptional payment. Likewise, a consistent pattern of overtime or commission over a 12-24 month period tells a clearer story than a short spike in earnings. Context, track record and employer structure all matter.

Many lenders have adapted their criteria to reflect this reality. For example, it is increasingly common for a proportion of annual bonus income to be considered within affordability calculations, often based on the most recent year or an average over time. Where there is a strong and evidenced long-term track record, underwriters may exercise discretion to use a higher proportion of that income.

Similarly, where a car allowance forms a regular contractual payment, lenders may consider up to 100% of it, subject to evidence that it is a consistent and ongoing part of remuneration. Overtime and commission can also be assessed more flexibly, particularly where the applicant has been in role for a sufficient period and can demonstrate a stable pattern of receipt.

Second jobs are another area where the market has evolved. With over a million people in the UK balancing more than one role, it is no longer unusual for applicants to have dual income streams. Where both roles have been worked concurrently for at least 12 months and sustainability can be demonstrated, many lenders will consider this income in full or in part.

Zero-hours and fixed-term contracts also require nuance. ONS data shows that while zero-hours contracts attract attention, they represent a relatively small proportion of the workforce overall. More importantly, many individuals on fixed-term contracts – particularly in sectors such as IT, education and healthcare – experience repeated renewals and long-term sector stability. When viewed in the context of employment history and earnings consistency, these cases can often be assessed sensibly rather than declined purely on employment type.

For brokers, the increasing prevalence of complex income reinforces the importance of case presentation. A clear income narrative, supported by payslips, P60s, contract details and employer confirmation where necessary, can significantly streamline underwriting. Early dialogue with Key Account Managers can also help clarify how specific income elements will be treated.

Complex income is not inherently higher risk. In many cases, it reflects ambition, adaptability and resilience. When assessed thoughtfully and evidenced properly, it can provide a strong foundation for sustainable homeownership.

Sources:
Office for National Statistics, Labour Market Overview, UK, 2024
HM Revenue & Customs, Self-Assessment Statistics

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