The cash conversion cycle (CCC) counts the days between paying your suppliers for stock and getting cash back from the customers who buy it. It is measured in days, and lower is better: a CCC of 60 means every dollar spent on stock is trapped for about two months before it returns, cash that cannot be used for anything else. The math: days stock sits on the shelf (DSI), plus days customers take to pay (DSO), minus days you take to pay your own suppliers (DPO).
That subtraction is why the number can go negative, and negative here is excellent. Picture a coffee shop: customers pay cash on the spot (DSO of 0), the beans sell within days (tiny DSI), but the bean supplier gives 30 days to pay the invoice (DPO of 30). The shop collects the customer's money weeks before it ever pays for the beans, so its suppliers are effectively funding the till. That is a negative CCC. Apple and Amazon run this at giant scale, Apple often around minus 50 to 70 days.
A negative or near-zero CCC means the business can grow without parking extra cash in day-to-day operations, a built-in advantage. A long positive CCC of 90 days or more means the opposite: every step of growth traps more cash, which must be funded with debt, new shares, or profits that could have gone elsewhere.
One limit: CCC is meaningless for businesses with no stock to cycle, like software, services, and banks. For those, DSO alone is the honest read.