An income statement runs top to bottom in six blocks: revenue, cost of sales, gross profit, operating expenses, operating profit, and net profit after interest and tax. Read it as a sequence of questions — how much did we sell, what did it cost to deliver, what did we keep, what did it cost to run the business, and what was left.
Most owners glance at the bottom line and close the document. The useful information is in the relationships between the lines, and it takes about four minutes to extract.
The six blocks
1. Revenue (turnover, sales)
What you invoiced for goods or services in the period. Excludes VAT — VAT is not your income.
Ask: is it growing, and where is it coming from? Revenue up 30% because one client doubled is a very different business from revenue up 30% across forty clients.
2. Cost of sales (direct costs)
Costs that vary directly with what you sold — stock, raw materials, direct labour, subcontractors, delivery.
The test: if you sold nothing this month, would this cost disappear? If yes, it belongs here. If no, it is an operating expense.
3. Gross profit
Revenue less cost of sales. The most important number on the statement, and the one most owners never look at.
Gross profit margin = gross profit ÷ revenue × 100
Ask: what is the margin, and is it moving? A margin sliding from 42% to 36% is a serious problem that a growing revenue line will hide completely.
4. Operating expenses (overheads)
The cost of running the business regardless of sales — rent, salaries, insurance, software, accounting fees, marketing.
Ask: which three lines are biggest, and are they growing faster than revenue? Overheads growing faster than sales is how a profitable business becomes an unprofitable one.
5. Operating profit (EBITDA or EBIT)
Gross profit less operating expenses. This is how the business itself performs, before financing decisions and tax.
Ask: would this business be worth buying on this number? It is roughly what a purchaser would look at.
6. Net profit
Operating profit less interest and tax. What is actually left.
Ask: how much of the operating profit is being consumed by interest? A business with strong operating profit and weak net profit has a debt problem, not a trading problem.
A worked example
| This year | Last year | Change | |
|---|---|---|---|
| Revenue | R4,200,000 | R3,400,000 | +23.5% |
| Cost of sales | (R2,562,000) | (R1,972,000) | +29.9% |
| Gross profit | R1,638,000 | R1,428,000 | +14.7% |
| Gross margin | 39.0% | 42.0% | −3.0 pts |
| Operating expenses | (R1,180,000) | (R980,000) | +20.4% |
| Operating profit | R458,000 | R448,000 | +2.2% |
| Interest | (R96,000) | (R62,000) | +54.8% |
| Tax | (R97,740) | (R104,220) | |
| Net profit | R264,260 | R281,780 | −6.2% |
Revenue grew 23.5% and net profit fell 6.2%. Three things caused it:
Gross margin dropped 3 points. Cost of sales grew faster than revenue — prices not raised, input costs up, or discounting to win the extra work. Restoring 42% would have added roughly R126,000 of gross profit.
Overheads grew 20.4% to support 23.5% growth. Not unreasonable, but it consumed most of the extra gross profit.
Interest rose 54.8%, presumably to fund the growth.
The lesson this statement teaches: growth funded by discounting and debt can leave you working considerably harder for less money. You would not see any of that from the revenue line alone.
The four numbers to check every month
1. Gross profit margin. The single most diagnostic number. Track it monthly and investigate any move of more than 2 points.
2. Overheads as a percentage of revenue. Should be stable or falling as you grow. Rising means you are adding cost faster than sales.
3. Operating profit margin. Operating profit ÷ revenue. Tells you whether the business model works.
4. Your three largest expense lines. In most small businesses, salaries, rent and one other account make up the majority of overheads. Watch those three and you are watching most of the cost base.
Reading it properly
Always compare. A single month tells you almost nothing. Compare against last month, the same month last year, and budget.
Watch percentages, not just rands. Every line as a percentage of revenue makes trends visible that absolute numbers hide.
Look for the line that moved. When profit changes materially, one or two lines almost always explain it. Find them.
Remember accounting profit is not cash. Depreciation reduces profit without touching cash, and loan capital repayments consume cash without touching profit. See why your bank balance is not your profit.
Remember it is not taxable income either. Depreciation is replaced by wear and tear, entertainment and fines are added back, and provisions are usually not deductible.
Frequently asked questions
How do I read an income statement? Read it top to bottom in six blocks — revenue, cost of sales, gross profit, operating expenses, operating profit and net profit — and ask what each one tells you. The most useful figures are gross profit margin and overheads as a percentage of revenue, tracked over time.
What is the difference between gross profit and net profit? Gross profit is revenue less the direct costs of delivering what you sold. Net profit is what remains after operating expenses, interest and tax. Gross profit tells you whether your pricing works; net profit tells you what you actually kept.
What is a good gross profit margin? It varies enormously by industry — retail and distribution run low margins on high volume, while services and software run much higher. What matters more than the absolute number is whether yours is stable or declining against your own history.
What is the difference between cost of sales and operating expenses? Cost of sales varies directly with what you sell — stock, materials, direct labour, delivery. Operating expenses are incurred regardless of sales — rent, admin salaries, insurance, software. The test is whether the cost would disappear if you sold nothing.
Is my income statement the same as my tax return? No. Taxable income is calculated from the income statement but differs from accounting profit, because depreciation is replaced by wear and tear allowances, entertainment and fines are added back, and provisions are generally not deductible until incurred.
How often should I look at my income statement? Monthly. Annual financial statements tell you what happened up to eleven months ago. Monthly management accounts tell you in time to do something about it.
Reports you can actually use
An income statement that arrives eleven months after the period, in accounting language, with no comparatives, is a compliance document. It is not management information.
Smartbook produces monthly management accounts with comparatives, margins and the lines that moved — in plain language, with a short note on what changed and why.
Last reviewed: 26 July 2026. Written by the Smartbook team — SAIPA and SAICA accredited, SARS registered tax practitioners. Worked examples are illustrative. General guidance, not advice on your circumstances.