What it means
A business serves two customers who each buy $100,000 of goods, but one needs custom packaging, emergency shipments and heavy support while the other orders predictable volumes. Looking only at invoice revenue hides their different economics.
Glacier Lake Partners describes gross margin by customer as a unit-economics lens on customer revenue and associated delivery costs, and Cost & Profitability distinguishes gross margin from a deeper cost-to-serve view, so that boundary must be stated before comparing customers. Choose the period, since a month can contain a large order but no matching return yet, and a rolling year may be fairer for seasonal buyers.
Identify the customer, because parent groups, subsidiaries and separate billing accounts can represent one economic relationship, so define the grouping and avoid double counting. Start with net revenue, including discounts, credits and returns under a consistent recognition policy, as headline invoiced sales alone can overstate the contribution.
Assign direct product cost, using the cost of goods or contracted service delivery that reasonably belongs to the customer's transactions, and reconcile it to financial accounts. Set the margin boundary: gross margin generally subtracts cost of goods sold, while a detailed customer-profitability calculation may subtract selling, service and distribution expenses as well.
Keep the stages separate by showing gross margin first and then additional customer-level service costs, because calling the latter gross margin can confuse managers and external readers. Understand allocations, as shared factory overhead may be assigned by units or machine time and the chosen driver can change customer rankings even though cash has not changed.
Distinguish avoidable costs, since a decision to stop serving a customer may not remove all allocated rent or salary, so calculate incremental profit for that decision separately. Track rebates and returns: volume incentives earned at quarter-end affect realised revenue and should be tied to agreements and settlement evidence, while credit notes can land after the original sale and belong to the appropriate customer and period rather than generic overhead.
Consider service contracts, where a customer may pay one annual fee while service work arrives unevenly, so match recognised revenue and delivery cost under the chosen method. Watch sales mix, because a large customer may buy mostly low-margin items and product families should be segmented before blaming the customer for the portfolio's structure.
Look at price realisation, since list price minus rebates, discretionary discounts and credits explains why two buyers of the same item earn different margins. Compare margins and dollars, as a high percentage on tiny revenue can contribute fewer gross-profit dollars than a lower percentage on a large order book, and check concentration, since the highest-margin customer may also dominate revenue and losing it can threaten the business.
Read the contract, because minimum volumes, price escalators, service levels and chargebacks can change future economics and historical margin does not prove next year's outcome. Use a bridge over time to show whether margin changed because of price, product mix, material cost or returns, because a percentage alone does not suggest an action; for an owner, customer gross margin is a first cut at the economics of a relationship, most useful when its cost boundary is explicit and the fuller cost-to-serve picture remains visible.
In practice
Real-world examples.
Example
One customer's $100,000 of net revenue and $65,000 of assigned cost produce $35,000 of gross margin, or 35%. The finance team compares it with the company average and finds the account in line. It then looks at the support cost below gross margin before deciding anything.
Example
Two buyers pay the same product price, but a return and credit note reduce one buyer's realised margin. The report shows both buyers side by side, with the credit assigned to the customer who returned the goods. The difference prompts a review of the order and the sales terms.
Example
A manufacturer separates account gross margin from the later cost of dedicated support and freight. The first view shows the product economics, while the second shows the cost of serving the account. Managers use both before agreeing a new price list.
Formula
Calculation
Customer gross margin = customer net revenue - cost of goods or direct delivery cost assigned under the stated method. Gross margin percentage = that margin / customer net revenue x 100.
Worked example. A customer has $100,000 of net revenue and $65,000 of assigned cost.
- Gross margin = $100,000 - $65,000 = $35,000.
- Gross margin percentage = $35,000 / $100,000 x 100 = 35%.
A second buyer purchases the same goods at the same list price, but receives a $5,000 rebate and $3,000 of returns credits, leaving $92,000 of net revenue. Assigned cost is also $65,000.
- Gross margin = $92,000 - $65,000 = $27,000.
- Gross margin percentage = $27,000 / $92,000 x 100 = 29.3%, so the same product earns a lower margin.Case study
Seen in the real world.
This entirely fictional example follows Harbor Components. Its largest account generated $1,000,000 of invoiced sales, but $40,000 of rebates and $60,000 of returns cut realised revenue to $900,000, while custom production raised assigned cost to $630,000. Gross margin was therefore $270,000, or 30%, rather than the 37% that invoiced sales alone would have suggested.
Finance separated gross margin from outbound freight of $45,000 and account-manager time of $35,000, leaving $190,000 after those service costs. It then reviewed an order-minimum proposal with sales. The case does not treat allocated head-office rent as an avoidable cost of the account.
Watch out
Common mistakes.
- Calling customer revenue customer profit without assigning related delivery cost.
- Mixing after-gross-margin support costs into one account's gross margin but not another's.
- Treating shared overhead allocated by an arbitrary driver as cash saved if an account leaves.
Questions
People also ask.
Is this the same as customer profitability?
No. Customer profitability can also reflect selling, service, distribution and other account-level costs.
Should revenue include discounts and returns?
Use net recognised revenue under a consistent policy, including appropriate credits.
Can a high-margin customer still be risky?
Yes. Concentration, payment behaviour and contract commitments matter beyond margin.
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