I think we sometimes treat a high salary—or a mortgage approval—as proof that a household is financially secure. They say something about income and affordability now. They tell you much less about how exposed the household would be if one income stopped.
Lenders can count bonus income when their criteria are met. The details vary. For example, Halifax says it uses the lower of the last 12 months’ total or the two-year average for bonus or commission paid less often than monthly. FCA rules also require lenders to consider future income changes they know, or should reasonably know, are likely. A mortgage affordability test can be thorough and still not tell you how a borrower feels about the risk of a sector-wide round of redundancies, or what it would mean to lose a second income. Halifax intermediary criteria · FCA MCOB 11.6.
This can be particularly visible in London, where housing can absorb a large share of income. The Office for National Statistics estimated average private rent in London at 41.6% of median private-renting household income in the financial year ending 2024. That is a regional average, not a measure of high earners or any one household, but it shows how a large income can come with large fixed commitments. ONS private rental affordability, FYE 2024.
Two incomes help, but they do not remove the pressure
Two incomes do offer more resilience than one. But many households now have two adults balancing paid work with a share of parenting and the mental load at home. That can mean more coordination and pressure on each person, even while the second income provides a buffer.
The opposite arrangement has its own strain. If one person is the sole breadwinner and works in an industry where roles or earnings can change quickly, the income risk is concentrated in one job. That can feel doubly stressful: the household depends on that income, and the person earning it may feel responsible for keeping everything going.
The risk is not always a low-paid month. If you budget, you may plan around expected earnings over the year, including a bonus that has been fairly consistent. The more serious question may be what happens if one person brings in no income for a sustained period. If a household depends on two pay packets, that could be your own or your partner’s.
Finding another job can still feel uncertain
Someone may have been in the same role for years and built up detailed knowledge of the organisation, its people and how work gets done. That knowledge has value, but it may not be obvious how much of it travels to another employer. Even if the person could find a new role, they may doubt their ability to explain their skills, rebuild a network or prove themselves somewhere new.
That uncertainty can create real anxiety for someone whose day-to-day lifestyle is affordable. The worry is not necessarily that the bills cannot be paid today. It may be that a single change at work would make the household draw on its reserves much faster than expected.
Runway depends on what you can reach
A household’s runway is more than the balance of its savings accounts. It also depends on how soon money can be accessed, what it might cost to use, and whether you would be willing to draw on it at that moment.
Cash is available without selling investments into a falling market. A cash ISA may be accessible too, depending on its terms. A share portfolio can often be sold quickly, but if income loss arrives alongside a market fall, you may prefer to wait before selling. There is no guarantee markets will recover on your timetable. Credit cards and overdrafts can provide short-term access, but borrowing has a cost and the lender can change the terms or limit.
MoneyHelper offers three to six months of essential outgoings as a general emergency-savings rule of thumb. That can be a useful reference, but it does not answer every household’s question. The more relevant test may be: if one income stopped, how long could you meet your commitments before needing to borrow, sell investments or change the way you live? MoneyHelper: emergency savings.
I have historically kept a relatively small emergency fund. I have relied on substantial credit-card and overdraft limits, then a smaller cash ISA I could draw on, before getting to my invested ISAs. Using debt to cover an extended gap would be expensive. But I have been willing to accept that risk while my earnings felt reasonably steady and replaceable, and when I expected not to need the credit most of the time. If our household moved to one income, I would look at it differently: more of the household’s security would depend on one person continuing to earn.
For me, financial security when you are young is less about eliminating every risk than living within your means and borrowing prudently. Housing is often the largest commitment. Choosing a smaller home than a lender might allow can leave more room if work or income changes. A good salary helps, but the space between what you earn and what you have committed is what gives you time to respond.