Debtor Days for Small Businesses: The Monthly 20-Minute Review That Prices Your Patience

Most small businesses know their revenue to the dollar and have no idea how long their money takes to come home. Debtor days is the bridge: the average number of days between sending an invoice and getting paid. It is the one number that decides whether growth is a gift or a trap — invoice $96,000 a month and wait 58 days, and you are permanently funding seven weeks of someone else's payroll.

The formula, run monthly on the same day:

Debtor days = (accounts receivable ÷ credit sales) × days in the period

$186,000 of receivables against $96,000 of monthly invoicing = 58 days. If your terms are net-14, customers are paying four times later than agreed — that is a decision someone is making, not weather. And a day is worth real money: one debtor day on that business is ~$3,200 of cash sitting in customers' accounts instead of yours.

The 20-minute monthly review — six numbers:

1. Receivables balance (last day of month)
2. Credit sales for the month
3. The ratio, written next to last month's
4. The aged breakdown — current / 1-30 late / 31-60 / 60-plus (the total can look stable while the 60-plus bucket doubles; the buckets are where the queue hides)
5. The largest three balances (if one customer is 40% of receivables, your payment schedule is one accounts-payable clerk's mood)
6. Days-to-invoice — the part you own, the most common reason a good payer looks bad

Then five minutes of decisions: 60-plus bucket growing → escalate those names today. Concentration above a third → deposit the next job. Days-to-invoice above three → that's this month's fix, not the customers'.

The two levers:

1. Invoice the same day the work is done. Work finished Tuesday and invoiced Monday has burned five days nobody negotiated for. On 58 debtor days with a 5-day lag, same-day invoicing is worth ~8% of the receivables balance before a single customer changes behaviour.
2. Chase on a schedule, not on a mood. Reminder day 7, polite-but-specific day 14, formal day 30. The business that chases when cash feels tight trains customers to pay the businesses that chase on schedule first.

The third lever is free with new customers: terms are set at onboarding — deposits on first jobs, short terms for strangers, never renegotiated under pressure.

The four traps: watching the total instead of the buckets; the growth illusion (sales +20% with flat debtor days = receivables +20%, growth you fund yourself); blaming the customer for the invoicing lag (half the "bad payers" are a lagging invoice queue); fixing the number once and never again.

The worked example. A commercial cleaning company, $96,000/month invoiced, receivables at $186,000 — 58 days on net-14 terms. One month of same-day invoicing (the lag had been 6 days), an automated day-7 reminder, one named day-14 letter to the three large balances, deposits on the two new contracts. Next review: receivables $108,000 — 34 days. The $78,000 difference funded payroll through a soft December without touching the overdraft. The owner: "We weren't being stiffed. We were just the last company on their list, every month, by default."

Full review (formula, six numbers, five decisions, the traps): Debtor Days for Small Businesses — HIVE80lab ops-notes