Customer Concentration Risk: Calculate Revenue Shares

Customer concentration describes how much of a business's revenue comes from individual customers. It helps identify which relationships deserve closer review, but a percentage alone does not establish a valuation discount, borrowing limit or risk grade.

Use the customer concentration report to calculate each customer's share, the largest customer's share and the combined share of the five largest customers. Start with a complete, reconciled customer revenue list for one period and one currency.

Define the Population Before Calculating​

Choose an inclusive start and end date. Use the same accounting basis and revenue definition for every customer, and reconcile the customer total to the revenue records for that period. Net revenue should reflect the returns, credits and other adjustments included in those records. Do not substitute cash receipts or unpaid invoice balances for revenue.

Include every customer in the chosen population, including small customers. Including only the largest accounts makes the denominator too small and overstates their shares. The report measures the data you supply; it cannot detect customers omitted from your source records.

Use a stable customer ID for each customer. IDs are required and case-sensitive; A and a identify different customers. Names are optional display labels, so two customers can have the same name without becoming one customer. If subsidiaries should be analyzed as one group, decide and document that grouping before preparing the input. The report does not infer ownership relationships.

The report accepts nonnegative net revenue, one row per customer ID, in a single currency. It performs no currency conversion. A negative customer total needs a separate reconciliation or analysis; do not delete a valid credit simply to force the data through this tool.

Worked Example: January 1–March 31, 2026​

This illustrative business has six customers and USD 1,000.00 of net revenue for the full first quarter of 2026. The optional names below match the IDs only to keep the example easy to follow.

Each share is the customer's net revenue divided by total net revenue. The largest customer is A: 600.00 ÷ 1,000.00 = 60.00%. The five largest customers are A through E: (600.00 + 200.00 + 100.00 + 50.00 + 30.00) ÷ 1,000.00 = 98.00%. Customer F remains in the denominator even though F is outside the top five.

With fewer than five customers, the top-five calculation includes all available customers. With zero total revenue, every share is undefined because division by zero has no percentage result. A valid all-zero report is different from an empty or invalid report. Displayed and exported shares use two decimal places; rounding can make displayed customer shares sum to slightly more or less than 100% in other examples.

Reproduce the Example in the Report​

Select Load example in the report, or save the following text as a UTF-8 CSV and choose it in the import panel. The first column is the record type; keep the header and date format as shown.

customer_concentration_v1,start_date,end_date,currency,customer_id,customer_name,revenue
customer,2026-01-01,2026-03-31,USD,A,Customer A,600.00
customer,2026-01-01,2026-03-31,USD,B,Customer B,200.00
customer,2026-01-01,2026-03-31,USD,C,Customer C,100.00
customer,2026-01-01,2026-03-31,USD,D,Customer D,50.00
customer,2026-01-01,2026-03-31,USD,E,Customer E,30.00
customer,2026-01-01,2026-03-31,USD,F,Customer F,20.00

File selection stages a preview. Review its period, currency, customer count and total, then select Apply import to replace the current inputs. Inspect the customer rows in the applied report. An invalid file leaves the current report unchanged. You can also enter or edit the rows manually.

Download the current valid report to keep its input rows and calculated columns together. Percentages in the CSV use numbers such as 60.00 to mean 60%. Reimporting a report recomputes its calculated columns from the inputs. The tool works locally in the browser and does not save a persistent copy of your draft; retain your own source records and downloaded file.

Revenue Concentration Is Different from Receivables Concentration​

Revenue concentration covers activity over a period. Receivables concentration covers amounts still owed at a particular date. Customer A could account for 60% of this quarter's revenue and owe nothing at quarter-end because every invoice has been paid. Another customer could have a smaller revenue share but a larger overdue balance.

The OCC's asset-based lending handbook discusses receivables collateral in terms of the customer base, concentrations, delinquency, dilution and credit quality. It describes concentration limits and possible adjustments to collateral eligibility or advance rates in that lending context. Those judgments concern receivables and lending terms; this revenue report does not calculate an eligible borrowing base. See the OCC handbook's accounts-receivable discussion, printed pages 16–17.

Keep an invoice-level aging report and the actual financing agreement alongside a revenue concentration analysis when reviewing a receivables facility. Do not apply a revenue percentage directly to an outstanding receivables balance or assume a standard loan haircut.

What the 10% Disclosure Threshold Means​

The often-cited 10% figure comes from a specific financial-reporting context. A FASB summary of ASC 280-10-50-42 describes disclosure when revenue from a single external customer reaches 10% or more of an entity's revenue: the fact, the revenue amount for each such customer and the segment or segments reporting that revenue. That provision does not require the customer's identity. See the current-GAAP column on page 47 of FASB's September 2018 meeting materials.

Topic 280 segment reporting applies to public entities within its scope; FASB's 2023 segment-reporting announcement describes that scope. This is not a blanket statement that every private business must publish its customer list when one account reaches 10%.

A concrete SEC example is its 2024 comment letter to Sanmina, comment 3. Staff asked for the net sales amount or percentage and relevant segments for customers comprising at least 10% of net sales in the presented periods, citing Topic 280.

A disclosure threshold identifies information that the applicable reporting rules require. It does not establish universal safe and unsafe revenue bands. The report therefore shows shares without assigning a risk grade, predicting a valuation discount or estimating loan capacity.

Turn the Figures into Specific Review Questions​

In the example, customer A supplies most revenue. The next step is to understand that relationship and the business's ability to absorb changes:

• Contracts: When does the agreement renew, and what termination or purchase-volume terms actually apply?
• Profitability: How much margin comes from that customer, and which costs would remain if revenue fell?
• Payment timing: Are invoices paid when due, and how much is currently outstanding?
• Shared exposure: Do apparently separate customers share an owner, industry or demand driver?
• Comparability: Did a changed period, acquisition, customer grouping or revenue policy alter the denominator?

Use documented assumptions for any customer-loss scenario or valuation analysis. A revenue share does not tell you the resulting profit or cash shortfall, and there is no guaranteed timetable for changing a customer mix. Compare consistent periods and review the underlying amounts as well as percentages: a lower share can reflect growth elsewhere or a decline in the largest customer's revenue.

For a broader view of valuation approaches, see the business valuation methods guide.

Keep a Reconciled Record for the Next Review​

Retain the period definition, customer-ID mapping, adjustments and reconciliation that produced the input rows. Keep links or references to the supporting invoices and accounting records. If you use plain-text bookkeeping, maintain those references consistently and prepare the customer totals from your records before entering them here. The report does not connect to your ledger or automatically create a customer revenue dashboard.

Return to the customer concentration report when the next period's complete figures are ready. For help organizing your bookkeeping workflow, use the Beancount help center; the concentration analysis remains a separate, reviewed calculation from the customer totals you provide.