Between the day you spend money to serve a customer and the day their payment lands, your business is quietly lending. To customers (receivables), to the shelf (inventory), offset a little by suppliers lending to you (payables). The net of that lending is working capital — cash that exists, works, and is never in your bank account. Owners who don't understand it experience its symptoms as a mystery: "we're growing, we're profitable, where is the money?" It's here. Trapped, on purpose or not.
A landscaping job: you buy $800 of materials Monday (cash out), pay the crew Friday (cash out), finish the job, invoice $2,500 on net-30 — and collect five weeks later. For five weeks, $1,600+ of your cash is parked inside one job. Run eight jobs a month like this and roughly $13,000 of yours is permanently out on loan — not lost, not spent: deployed as inventory and receivables. That parked amount is your working capital requirement, and it has two brutal properties:
It scales with revenue. Double the jobs, double the cash parked. This is the mechanical reason growth eats cash (the profit-is-not-cash and payback lessons keep colliding with it): every new dollar of monthly revenue demands its slice of float up front. Growth planning that only models profit misses the loan you must extend to your own expansion.
It's set by three timing dials. How fast customers pay you (receivable days), how long stock sits before selling (inventory days), and how fast you pay suppliers (payable days). Roughly: cash is trapped for receivable days + inventory days − payable days. Shrink the first two, stretch the third, and cash flows back out of the structure — without selling one more job.
Receivables (the big one for service businesses): deposits up front, invoice the day work completes (not month-end), shorter terms, card on file, prompt-pay nudges. The get-paid-faster lesson is the full playbook — every day cut from average collection frees (daily revenue × 1 day) of cash, permanently.
Inventory (the big one for product businesses): order closer to demand, smaller more frequent buys, kill the slow movers (the report is in your bookkeeping software; the dead stock on the top shelf is working capital in costume). Every week of inventory you don't hold is cash back in the account.
Payables: take the full terms you're given — paying net-30 invoices on day 5 is donating float. Stretch respectfully (ask for net-45; suppliers often say yes to good payers), never destructively: your suppliers' patience is capacity you'll want in a crunch, and early-pay discounts (like 2% for paying in 10 days) are often worth taking — that's a separate, deliberate trade in the pay-smart lesson.
Or restructure the model itself — the deepest fix: deposits and progress billing on big jobs, prepaid packages, retainers, subscriptions. Every dollar collected before delivery is working capital you never have to fund. Some businesses (gyms, insurers, prepaid anything) run negative working capital — customers fund the operation. That structural advantage is worth designing toward where your market allows it.