Net income is the number that leads the press release. Free cash flow is the number that pays for buybacks, dividends, and everything a company does without asking shareholders for more money. When the two disagree, the second one is usually telling the truth.
The difference in one line
Net income is an accounting opinion about a period. Free cash flow is what actually landed in the bank after the business paid to keep itself running. Both are legitimate. But net income is assembled from judgment calls — when to recognise revenue, how fast to depreciate an asset, what to treat as a one-off — and cash is not.
Why they come apart
A gap between profit and cash isn't fraud, and it isn't rare. The common causes are mundane, and each one tells you something specific about the business:
- Heavy capital spending — profit is reported now, the cash left years earlier or is leaving now.
- Growing receivables — the sale is booked, the customer hasn't paid.
- Inventory build — cash converted into goods sitting in a warehouse.
- Stock-based compensation — an expense that reduces profit without moving cash, while quietly diluting you.
- Depreciation of assets bought long ago — a charge against profit with no cash attached at all.
Notice that the last two run in opposite directions. Depreciation makes cash flow look better than profit. Stock compensation makes cash flow look better than profit too — but for a reason that costs you real ownership. This is why free cash flow on its own is not a purity test.
The pattern that should worry you
A single year where profit exceeds cash flow means very little. Companies invest in bursts, and a big capex year is often a good sign. What matters is the multi-year relationship. If net income has risen steadily for five years while free cash flow has stayed flat or gone backwards, something structural is absorbing the profit before it reaches you.
The usual culprits are working capital that grows faster than sales, or maintenance spending that was quietly deferred and is now coming due. Neither shows up in an earnings headline. Both show up immediately if you put five years of net income and five years of free cash flow side by side.
Where cash flow lies too
Free cash flow has its own failure mode, and it's the mirror of the one above. A company can produce excellent free cash flow for several years simply by not investing — cutting capital spending, stretching payment terms with suppliers, running assets past the point where they should have been replaced. The cash looks great right up until the bill arrives.
So read the two together rather than picking a favourite. Profit without cash means the earnings may not be real. Cash without investment means the earnings may not last.
How we use it
Investily scores free cash flow growth as its own component precisely because it disagrees with reported profit often enough to be informative. We also measure returns on capital in cash terms alongside the accounting version, which surfaces the gap directly — a company whose cash-flow returns sit far below its accounting returns is converting profit into something other than cash, and that's worth a look before you buy it.
The bottom line
Treat net income as the claim and free cash flow as the evidence. Most of the time they agree and there's nothing to investigate. When they diverge for more than a year or two, the divergence is the story — and it is almost always more informative than whatever the earnings headline said. The related question of whether the capital producing that cash is earning enough is answered by return on capital employed.