Operating cash flow comes from the cash flow statement, usually tagged NetCashProvidedByUsedInOperatingActivities in XBRL, and is typically measured over a full fiscal year or the trailing twelve months. Total liabilities come from the balance sheet, tagged Liabilities. The ratio is calculated from figures reported in SEC filings. Many companies do not present a total liabilities line at all, showing only total liabilities and equity, in which case the figure is derived by subtracting total equity from that combined total. Some analysts average the opening and closing liability balances to match the period over which the cash was earned.
Total liabilities is a much broader base than debt. It includes accounts payable, accrued expenses, deferred revenue, lease liabilities, pension obligations, and deferred taxes, some of which will never require a cash payment in the usual sense. A software company with large deferred revenue can look weaker on this ratio than its debt load suggests, so it helps to compare it with debt-focused measures such as total debt to EBITDA.
Credit analysts use the ratio to judge whether a company's operations can carry its obligations without refinancing. It is less useful for banks and insurers, whose liabilities are mostly customer deposits and policy reserves that fund their business rather than burden it. A negative ratio means operating cash flow was negative for the period and the company relied on outside financing or existing reserves.