Client Concentration Risk Calculator

This is not a hypothetical risk

On r/smallbusiness, one owner described a maintenance business built over almost 15 years where a single account had grown to make up more than 90% of income. When the client hired a new manager and brought the work in-house, that revenue disappeared in a week — along with one of the owner's few employees. A top comment on that thread put it plainly: a business like that should never rely on a single customer. In the same discussion, another owner mentioned running roughly $1.5M in revenue with one client accounting for 98% of it — workable only because the operation was almost entirely automated.

Elsewhere on r/Solopreneur, an agency owner lost a client worth about 40% of annual revenue (roughly $50,000) after a single unresolved complaint sat unnoticed online for three weeks before a competitor stepped in. None of these owners set out to be this dependent on one client — concentration tends to creep up gradually, one good year at a time, until it's the whole business.