Revenue on your P&L doesn't pay the bills until the cash actually lands. One number tells you how long that gap is: days sales outstanding, or DSO. How to figure it: take what customers owe you right now (your accounts receivable), divide it by last month's sales, and multiply by 30. Example: customers owe you $12,000 and you sold $20,000 last month. $12,000 / $20,000 x 30 = 18 days. What it means: if your terms are "due in 15 days" and your DSO is 18, you're close. If it's 45, you're lending your customers money for free, and that's usually where a cash crunch comes from even when sales look great. One thing to do today: pull your open invoices, sort them oldest first, and send a friendly reminder on anything past due.