Working capital is the difference between a company's current assets and its current liabilities. It represents the net amount of short-term resources available to fund day-to-day operations after all short-term obligations are accounted for. A positive working capital means the company has more short-term assets than short-term debts; a negative working capital means short-term debts exceed short-term assets.
Working capital is not a ratio — it is a dollar amount, which makes it most useful when tracked as a trend over time or compared to revenue. A company whose working capital is declining quarter over quarter may be burning through liquidity, while growing working capital may indicate improving financial health or an accumulation of inventory that is not converting to sales.
Negative working capital is not always a bad sign. Companies with strong bargaining power — like Amazon, Walmart, and Costco — routinely operate with negative working capital because they collect cash from customers before they have to pay suppliers. This means they effectively use their suppliers' money to fund operations, which is actually a sign of operational efficiency.