Key Takeaways
- Gross profit margin equals gross profit divided by revenue, expressed as a percentage, isolating the entity's core production or procurement efficiency from operating overheads.
- A year-on-year shift exceeding 2–3 percentage points without an identified cause should trigger investigation under ISA 520.7.
- Misclassifying operating expenses as cost of sales (or the reverse) inflates or deflates the margin without affecting net profit, making the error invisible to bottom-line analysis.
- The margin is one of the first ratios auditors calculate during planning because it connects two of the most material line items on the income statement.
What is Gross Profit Margin?
The formula is gross profit divided by revenue, multiplied by 100. Both figures sit on the statement of profit or loss. IAS 1.99 permits (but does not require) an entity to present cost of sales as a separate line item when using the function-of-expense method. When the entity uses a nature-of-expense presentation, cost of sales does not appear as a distinct line, and the auditor must reconstruct it from raw material consumption, production wages, depreciation of production assets, and energy costs before a meaningful margin can be calculated.
ISA 520.5 requires the auditor to develop an expectation precise enough to identify a misstatement at the relevant materiality level. For gross profit margin, the expectation accounts for changes in input prices and product mix, as well as foreign exchange effects on imported raw materials. A flat year-on-year comparison is insufficient if the entity launched a lower-margin product line or renegotiated supplier contracts. ISA 520.7 requires investigation of any difference that exceeds the documented threshold.
The ratio also serves as a fraud indicator. An entity that reports stable revenue growth with an improving gross margin in a period of rising input costs is either genuinely outperforming its peers or misclassifying costs. ISA 240.A43 identifies unusual changes in gross margin as a risk factor for fraudulent financial reporting.
Worked example: Bergstrom Skog AB
Client: Swedish forestry and paper products company, FY2025, revenue EUR 75M, IFRS reporter. Bergstrom sells bleached pulp to European paper mills and reports cost of sales using the function-of-expense method.
Step 1 — Extract the relevant line items
Bergstrom's draft statement of profit or loss shows revenue of EUR 75.0M and cost of sales of EUR 54.8M. Gross profit is EUR 20.2M.
Step 2 — Calculate the current-year margin
EUR 20.2M divided by EUR 75.0M produces a gross profit margin of 26.9%. Compare to FY2024 (revenue EUR 68.4M, cost of sales EUR 48.1M, gross profit EUR 20.3M, margin 29.7%). The decline is 2.8 percentage points.
Step 3 — Set the expectation and threshold
The team expected the margin to remain within 1.5 percentage points of the prior year (range: 28.2%–31.2%), based on stable product mix and a 4% budgeted increase in wood fibre costs offset by price increases passed to customers. The actual margin of 26.9% falls 1.3 percentage points below the lower bound. Flag for investigation per ISA 520.7.
Step 4 — Investigate the deviation
The 2.8-percentage-point decline traces to two causes. Wood fibre costs increased by 11% (EUR 3.4M above budget) following supply disruptions in northern Finland during Q2 2025. Bergstrom passed through only 5% in price increases to customers, absorbing EUR 1.9M in the margin. Separately, a new containerboard product launched in Q3 2025 carries a 19% margin (versus 30% for core pulp), contributing EUR 6.2M of revenue at the lower margin and diluting the blended figure by 0.8 percentage points.
Conclusion: the gross profit margin of 26.9% is defensible because the deviation from the prior year is fully explained by documented input cost increases and the dilution effect of a lower-margin product launch.
Why it matters in practice
Teams frequently accept the gross profit margin at face value without testing whether the entity's classification of expenses between cost of sales and operating expenses has been applied consistently. IAS 1.99 does not prescribe which costs must be included in cost of sales, so an entity that shifts warehouse depreciation from cost of sales to distribution expenses in year two will report an improved margin with no change in underlying economics. The auditor must compare the composition of cost of sales year-on-year, not just the total.
Margin analysis often uses a single blended percentage for the entity as a whole. When the entity sells products at materially different margins, a blended analysis can mask offsetting movements: one segment's margin collapse is hidden by another segment's improvement. ISA 520.5(a) requires the auditor to consider whether the analytical procedure is suitable for the assertion, and a blended margin is not suitable when the product mix has changed.
Gross profit margin vs. net profit margin
| Dimension | Gross profit margin | Net profit margin |
|---|---|---|
| What it measures | Revenue minus cost of sales only, isolating production or procurement efficiency | Revenue minus all expenses (operating, financing, tax, and one-off items), measuring overall profitability |
| Where costs sit | Only costs directly attributable to producing or purchasing goods sold | All costs recognised in the period |
| Sensitivity to cost classification | Highly sensitive: reclassifying an expense between cost of sales and operating costs changes the margin | Insensitive: reclassifying between cost lines does not change the bottom line |
| Audit use | Detecting misstatements or misclassifications in revenue and cost of sales | Detecting misstatements across the full income statement, including financing and tax |
| Manipulation risk | Shifting costs out of cost of sales to inflate the margin while total expenses stay unchanged | Timing of expense recognition (e.g., deferring marketing costs to a future period) |
The distinction matters because a stable net profit margin can conceal a deteriorating gross margin offset by reduced operating expenses. An auditor who tracks only net margin may miss a classification shift between cost of sales and operating expenses that flatters gross margin without changing the bottom line.
Related terms
Frequently asked questions
How do I set a threshold for gross profit margin in analytical procedures?
Tie the threshold to performance materiality. If performance materiality is €500,000 and revenue is €75M, a margin shift of 0.67 percentage points equates to that amount. ISA 520.5(c) requires documentation of why the chosen threshold produces the precision needed. Most teams round to the nearest half percentage point.
Does gross profit margin apply to service companies with no cost of sales?
Service entities that present expenses by nature under IAS 1.99 do not report a cost of sales line item. The auditor can construct an equivalent by isolating direct service delivery costs (staff costs, subcontractor fees) from overhead. However, ISA 520.5(a) requires the auditor to assess whether the constructed ratio is reliable enough to serve as a substantive procedure. If the allocation between direct and indirect costs is subjective, the procedure may lack the precision ISA 520 demands.
When should I disaggregate gross margin by segment or product line?
Whenever the entity operates in segments with materially different margin profiles. IFRS 8.23 requires disclosure of segment revenue and segment profit or loss, which gives the auditor a ready-made dataset for disaggregated analysis. ISA 520.A11 notes that disaggregated data generally increases the effectiveness of analytical procedures by reducing the risk that offsetting misstatements go undetected within a blended total.