When a significant portion of sales depends on a customer, losing that order can affect the entire business. The problem is not just about turnover: staff, stocks or equipment can remain organized around a specific business relationship.
To read the concentration I propose to observe revenues, margins and receivables from the main customers. The three rankings may differ. A customer who buys a lot could generate a small margin or require particularly long payment times.
A hypothetical example is an order that occupies a large part of the production capacity. Before accepting its expansion, it is necessary to understand what other orders it will give up and how easily resources can be used elsewhere. Convenience also depends on the alternatives available.
Diversifying takes time and commercial costs. It does not mean immediately replacing an advantageous relationship, but knowing the exposure and preparing realistic possibilities. Periodic verification can link order trends, credit deadlines, and committed capacity. The useful question is what customer change would be difficult to absorb and what actions can reduce that fragility before it manifests itself.