Reading an Income Statement

A balance sheet is a photograph of one date. An income statement is a video covering a whole quarter or year: how much a company sold, what it cost to sell it, and what remained for the owners once every bill was paid. Where the balance sheet answers "what do you have," the income statement answers "how did you do."

The walk from revenue to profit

Every income statement follows roughly the same staircase, each step subtracting a different kind of cost.

Start with revenue — everything the company billed customers for goods or services delivered in the period. Subtract cost of goods sold (COGS), the direct cost of producing what was sold, to get gross profit. Subtract operating expenses — R&D, sales and marketing, general and administrative costs — to get operating income, often called EBIT (earnings before interest and taxes). Subtract interest expense (the cost of the company's debt) and add or subtract other non-operating items to get pre-tax income. Subtract taxes and what's left is net income, the number that ultimately belongs to shareholders.

$$\text{Net Income} = \text{Revenue} - \text{COGS} - \text{OpEx} - \text{Interest} - \text{Taxes}.$$

In words: every layer of the statement strips out a different group of claimants — suppliers, employees and marketers, lenders, and the government — in that order, before shareholders see what's left.

A worked example

A software company reports revenue of $500m. COGS (hosting costs, support staff) is $100m, so gross profit is $400m — an 80% gross margin, typical for software since there's little marginal cost to serve one more customer. Operating expenses run $280m (R&D $120m, sales and marketing $110m, G&A $50m), leaving operating income of $120m. The company carries $300m of debt at 5%, so interest expense is $15m, giving pre-tax income of $105m. At a 21% tax rate, taxes are $105 \times 0.21 \approx 22$ (in millions), i.e. $22m, leaving net income of $83m.

Two ratios fall straight out. Operating margin is $120/500 = 24\%$: for every dollar of revenue, 24 cents survives as operating profit before financing and taxes. Net margin is $83/500 \approx 16.6\%$: the fraction of each revenue dollar that ultimately reaches shareholders.

What analysts actually watch

Revenue growth and gross margin trends tell you about the underlying business; operating margin tells you about cost discipline; net margin gets noisy fast because it's exposed to one-off items — a lawsuit settlement, a tax law change, a debt refinancing — that have nothing to do with how the core business is performing. That's exactly why analysts also track EBITDA and adjusted earnings, which strip some of that noise back out.