The bank balance is the last place a cash crisis shows up, not the first. By the time cash visibly drops, the underlying operational signals have usually been firing for a month or two. The signals worth tracking are the ones a bookkeeper can pull from the books today.
Vendor terms creep is the quietest and earliest. When suppliers tighten payment expectations — Net 30 slipping to "we'd like to see payment in 14 days," late notices arriving earlier each month, requests for partial payment up front — they have noticed something about your paying pattern and want out ahead of it. Track the day-of-month each vendor invoice is paid against the agreed terms. If the median is sliding toward the due date instead of well before it, that is a real signal even when every check still clears.
The 60+ bucket of accounts receivable is the second. Aging splits unpaid invoices by how long they have been outstanding: current, 31 to 60, 61 to 90, and over 90. When the 61-to-90-and-over share of total receivables grows week over week for three weeks in a row, the collections cycle is slowing down — and a slowing collections cycle shows up as a cash problem about 30 days later when those invoices would have normally been paid.
Customer concentration is the third. If more than 30 percent of monthly revenue comes from a single customer, losing that customer is not a setback, it is a crisis. Watch the share each month; a steady creep toward concentration is itself a signal, even before the customer churns.
Owner draws outpacing profit is the fourth. Many small businesses pay the owner out of cash, not out of profit. When withdrawals consistently exceed reported net income month after month, the owner is subsidizing personal cash flow from business cash, and the books will eventually surface that as a balance issue.
Payroll above 40 percent of revenue, sustained, is the fifth. Service businesses can run higher briefly; product and distribution businesses generally cannot. Crossing 40 percent and staying there, with no plan to bring it down through revenue or headcount, is the most common setup for a small-business cash crunch.