How Much of Your Revenue Could Vanish in One Phone Call

A customer stopping its orders is a sales event.

But if that call forces you to redraw the production plan, refinance working capital and reconsider investment decisions, the issue is no longer lost revenue.

It is dependency.

Most companies know who their largest customer is. Far fewer know how much power that customer holds over the operating system of the business.

What the Data Reveals

The evidence is best read in three layers: a broad academic sample, a recent manufacturing study, and a planned Türkiye-specific dataset.

1. The broad academic sample

A PLOS ONE study examined 2,555 listed firms and 12,365 firm-year observations from the Shanghai and Shenzhen markets between 2008 and 2018. Customer concentration was measured through the sales share of major customers and a customer Herfindahl-type concentration index. Across the sample, sales to major customers averaged 13.6%, while the average customer concentration index was 5.1%. [1][2]

The important finding was not the average. It was the shape of the relationship.

Customer concentration did not produce a simple, linear outcome.

At moderate levels, major customers could support information sharing, operational planning and access to resources. As concentration became excessive, bargaining power shifted, switching costs rose and suppliers became more conservative in risk-taking, R&D, capital expenditure and financial policy. The study reported inverted-U relationships across risk-taking, investment and firm performance. [1]

2. The manufacturing check

A 2026 study of manufacturing firms listed in the Korean market over 2013–2024 reached a more direct conclusion:

Higher customer concentration was associated with lower supplier profitability.

The study attributes the result to the stronger bargaining position of major customers over price, payment terms and commercial concessions. It also reports that foreign ownership can mitigate part of the negative effect through stronger monitoring and advisory capacity. [3][4]

3. The Türkiye dataset

The third layer is a Türkiye-specific study to be built from the 2021–2025 financial statements and notes of 30–50 manufacturing companies listed on Borsa Istanbul.

The target sample will cover packaging, plastics and chemicals, paper and board, metals, automotive and white-goods suppliers, textiles, food, machinery and equipment. The source base will be the Public Disclosure Platform (KAP), which provides access to financial reports and historical disclosures. [5]

IFRS 8 provides the disclosure threshold: when revenue from a single external customer reaches 10% or more of total revenue, the entity must disclose the fact, the total revenue from that customer and the relevant operating segment or segments. The customer's identity does not have to be disclosed. [6]

For comparative management analysis, the Türkiye study will use the following concentration bands:

Customer share

Management classification

Below 10%

Distributed customer base

10%–20%

Concentration to monitor

20%–30%

High concentration

Above 30%

Critical customer dependency

Only the 10% threshold comes from IFRS 8. The other bands are analytical categories for this management framework, not official accounting, audit or regulatory risk classifications.

The analysis will examine profitability, collection periods, inventory, working-capital intensity, sales growth and export exposure. No empirical result from the planned BIST dataset is asserted until the collection and validation process is complete.

When Did Your Customer Start Running the Company?

The sales team stops expanding the market and starts protecting the order flow of one major account.

Production changes the schedule for that customer's urgency rather than plant-wide efficiency.

Finance stops treating extended terms as an exception and begins treating them as the price of the relationship.

Quality, procurement and logistics gradually create a separate rulebook for the same customer.

Investment decisions are no longer based on where the market is heading, but on the assumption that one customer will stay.

In management meetings, the question shifts from "Is this decision right?" to "How will the customer react?"

Terms that should be challenged are accepted. Requests that should be refused are postponed. Margin that should be defended is surrendered.

At that point, the customer is no longer just a large source of revenue. It is setting priorities, allocating resources and defining the boundaries of management action.

The real danger of customer concentration begins when the company loses its management will long before it loses the customer.

From Insight to Instrument

To manage that risk, I use a model I developed and refined through executive responsibility across the companies in which I have served: the One-Call Risk Score (OCRS). It is the English-language articulation of the Tek Telefon Risk Skoru (TTRS).

OCRS is built on a simple premise: customer dependency cannot be understood through revenue share alone. It must be measured across profit, cash, operations, decision freedom and replacement time.

The model evaluates every major customer across six dimensions:

Dimension

Weight

Management question

Revenue dependency

15%

How much of total sales would disappear?

Profit dependency

15%

How much gross profit is concentrated in the account?

Cash dependency

15%

How much of receivables and collection risk sits with the customer?

Operational dependency

20%

How much capacity, stock, tooling, equipment and labour are customer-specific?

Decision dependency

20%

Can the company still say no on price, terms, production and investment?

Replacement time

15%

How long would it take to replace the lost revenue and capacity utilisation?

Each dimension is scored from 0 to 100. The weighted total produces the customer's One-Call Risk Score.

0–24

25–49

50–74

75–100

Manageable

Monitor

High dependency

Critical dependency

A single score is not enough, however. Management must also see why the score is rising. OCRS therefore operates through three KPI sets.

Customer-level KPIs

Revenue share, gross-profit share, receivables share, actual collection period, capacity use, customer-specific inventory, unrecovered customer-specific investment and replacement time.

Portfolio KPIs

CR1, CR3 and CR5; customer HHI; contribution from new customers; the share of growth generated by existing major accounts; and the proportion of lost revenue replaced by new business.

Organisational KPIs

Deferred price increases, non-standard payment terms, production-plan changes, exceptions in quality or logistics, management decisions reversed after customer pressure, and sales time allocated to new-customer development.

Dependency appears in organisational behaviour before it becomes obvious in the financial statements.

A one-page board report should answer three questions:

How much value does this customer carry?
Which company resources are tied to it?
How quickly could the business replace the gap if the customer left?

The purpose of OCRS is not to make large customers smaller.

It is to show where the company has made itself smaller in front of a customer.

A Company Does Not Begin to Fail When It Loses a Customer. It Begins When Fear of Losing That Customer Stops It from Building Alternatives and Ties Its Fate to One Phone Call.

Large customers can help a company scale. But no commercial relationship is valuable enough to justify surrendering the ability to make independent decisions.

Management's responsibility is to build a company that can survive the customer's absence: by developing new accounts, creating alternative channels, avoiding irreversible customer-specific capacity commitments and making every commercial exception visible.

The question behind the One-Call Risk Score is deliberately simple:

What happens if that call comes today?

Does the company miss a sales target?

Does a production line fall idle?

Or does the entire organisation have to be rebuilt around the loss?

If the answer is not already in front of the management team, the risk has not disappeared.

The phone simply has not rung yet.

Editorial Note

This article provides a general management assessment of customer concentration, customer dependency and the effects that major customers may have on a company's financial structure, operations and decision-making system.

The academic findings, financial-reporting requirements and public-market information referenced in the article are based on the published studies and public sources listed below. Nothing in this article constitutes a company-specific review, independent audit, valuation, credit rating, investment recommendation, legal opinion, tax advice, accounting advice or formal enterprise-risk report.

The 10% figure discussed in the article is the major-customer disclosure threshold in IFRS 8. The other concentration bands and all OCRS risk ranges are management classifications created for comparative analysis. They are not official accounting, auditing, regulatory or financial-reporting thresholds.

The proposed 2021–2025 BIST Manufacturing Customer Concentration Dataset is a planned original research project based on publicly available financial statements and notes. Until data collection, validation and analysis are complete, no statement about that dataset should be read as a final empirical finding or as an assessment of any named company.

The organisational patterns described in the article are general management observations and do not identify or refer to any particular natural or legal person.

The One-Call Risk Score (OCRS) — the English-language articulation of the Tek Telefon Risk Skoru (TTRS) — was conceived and developed by Orkun Akçasarı and refined through application in companies where he held executive responsibility.

The model name, abbreviations, conceptual framework, six-dimensional architecture, weighting system, risk bands, customer-level, portfolio and organisational KPI structure, terminology, written formulation and visual presentation form part of Orkun Akçasarı's original intellectual work.

OCRS is a management and early-warning tool. It is not presented as a definitive scientific, statistical, legal, accounting or regulatory standard. Any implementation should be adapted to the company's industry, business model, contractual structure, customer portfolio, financial position and risk appetite.

Reproduction, adaptation, conversion into training or consulting material, commercial use, or presentation of the model or distinctive portions of this article as another person's original work should not occur without clear attribution and the author's permission, subject to applicable law.

Suggested attribution:

Source: Orkun Akçasarı, "How Much of Your Revenue Could Vanish in One Phone Call?" — One-Call Risk Score (OCRS) / Tek Telefon Risk Skoru (TTRS).

© 2026 Orkun Akçasarı. All rights reserved.

The terms "One-Call Risk Score," "OCRS," "Tek Telefon Risk Skoru" and "TTRS" are not presented with the ® symbol in this publication. Trademark and industrial-property protection should be assessed independently under the applicable registration framework.

Sources

1. Gao, D., Ma, J. & Wang, Y. (2021). "Does the Risk of Major Customer Need to Be Balanced? The Role of Customer Concentration in Corporate Governance." PLOS ONE, 16(11), e0259689.
Main academic study: 2,555 firms, 12,365 firm-year observations, 2008–2018; descriptive statistics and non-linear findings on customer concentration.
https://doi.org/10.1371/journal.pone.0259689

2. PLOS ONE Supporting Information — S1 File: Data.
Supporting data file associated with Gao, Ma & Wang (2021).
https://doi.org/10.1371/journal.pone.0259689.s001

3. Kim, S. E. (2026). "The Impact of Customer Concentration on Corporate Profitability." Journal of Economics, Finance and Management Studies, 9(4), 2127–2133.
Study of Korean listed manufacturing firms over 2013–2024.
https://doi.org/10.47191/jefms/v9-i4-43

4. Zenodo record for "The Impact of Customer Concentration on Corporate Profitability."
Open archival record and article file.
https://doi.org/10.5281/zenodo.19944834

5. Public Disclosure Platform (KAP) — General Information.
Official platform for public disclosures and historical financial reports of Borsa Istanbul companies.
https://www.kap.org.tr/en/about/general-information

6. IFRS Foundation. IFRS 8 — Operating Segments, paragraph 34: Information about Major Customers.
Official standard text covering the 10% major-customer disclosure threshold and identity disclosure rule.
https://www.ifrs.org/content/dam/ifrs/publications/html-standards/english/2025/issued/ifrs8.html

7. Republic of Türkiye — Law No. 5846 on Intellectual and Artistic Works.
Official legislation source relevant to protection of original written expression.
https://www.mevzuat.gov.tr/mevzuatmetin/1.3.5846.pdf

8. Republic of Türkiye — Industrial Property Code No. 6769.
Official legislation source relevant to trademarks and industrial-property rights.
https://www.mevzuat.gov.tr/mevzuatmetin/1.5.6769.pdf

9. Turkish Patent and Trademark Office — Trademark Search.
Official search portal for trademark records and preliminary name checks.
https://www.turkpatent.gov.tr/tr/arastirma-yap