Working capital, and why it eats cash
By SuperdayReps · Wharton MBA · ex-Greenhill · investment banking interview coaching
7 min read · updated July 2, 2026
Here's the thing nobody tells you in your first accounting class: a company can be growing fast, booking record profits, and still run out of cash. Not because it's losing money. Because its cash is stuck inside the business.
That stuck cash is working capital. Understand it and you understand why profit and cash are two different animals, which is the single idea that separates people who "get" the three statements from people who memorized a script.
What working capital actually is
Net working capital (NWC) is the money tied up in the short-term stuff you need to operate. The clean definition bankers use:
Note the word operating. We deliberately strip out cash and any short-term debt. Cash is what we're trying to explain, not part of the tangle we're measuring. Debt is a financing decision, not an operating one. So the real line items are:
| Operating assets (uses of cash) | Operating liabilities (sources of cash) |
|---|---|
| Accounts receivable (AR): sales you booked but haven't collected | Accounts payable (AP): bills you owe suppliers but haven't paid |
| Inventory: product sitting on shelves | Accrued expenses: wages, rent, etc. owed but not yet paid |
| Prepaid expenses: things you paid for early | Deferred revenue: cash collected before you deliver |
The mental model: assets are cash you've handed out and are waiting to get back. Liabilities are cash other people have handed you and you're sitting on. That framing tells you which way the cash moves, and it's the part beginners flip.
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Frequently asked
- What is working capital?
- Net working capital is the cash tied up in running the business day to day: current operating assets minus current operating liabilities. You strip out cash and short-term debt, so the real line items are receivables and inventory against payables, accrued expenses, and deferred revenue. It is why profit and cash are two different animals.
- Why does growing working capital drain cash?
- Because every extra dollar of receivables is cash a customer owes you but has not paid, and every extra dollar of inventory sits in a warehouse instead of your account. An increase in an operating asset uses cash. Fast-growing companies keep widening that gap, which is how a profitable quarter can turn cash-negative.
- What is the cash conversion cycle?
- The cash conversion cycle measures how many days your cash is locked up, from paying for inventory to collecting from the customer. It equals days inventory outstanding plus days sales outstanding minus days payable outstanding. You want to sell fast, collect fast, and pay suppliers slowly, so a shorter cycle frees up cash.
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