Competency confusion is mistaking one kind of ability for another — usually assuming that being good at the work means being good at the business built on it.

The standard case

An excellent developer, designer or consultant goes independent. The technical work is not the problem and never was. The problem is pricing, sales, positioning, cash management and hiring — a set of skills that share no overlap with the one that justified the decision.

Competence in the craft produced the confidence to leave and supplies none of the capabilities required afterwards. The gap is usually discovered during the first cash shortage rather than in advance. See The E-Myth Revisited.

The other directions

Adjacent competence. Being good at one part of a discipline and assuming the rest. Strong delivery does not imply strong sales, even inside the same trade.

Borrowed competence. Performing well inside an organization whose systems, brand and pipeline were doing more of the work than was visible. The capability was real and partly belonged to the environment, which is why it does not always transfer. See career capital.

Confidence mistaken for competence, in both directions. People with deep knowledge see the parts they have not mastered; people with shallow knowledge see a complete picture. Certainty is a poor signal of ability and is the one most readily available to observers.

Catching it

The reliable test is an outcome rather than a judgment. Can you point to a result this capability produced, without the support of an organization? Have you done it more than once, and could you do it again on demand?

The useful move when you find a gap is to name it specifically. "I cannot sell" is not a diagnosis. "I do not know how to price, and I avoid the conversation where it is raised" identifies the thing to fix. See revealed preference.

The promotion case has its own name and is worth knowing separately. The Peter principle holds that people rise until they reach a job they are not good at, because a promotion is a reward for evidence about a different role. It is competency confusion with an organization doing the confusing on your behalf, and it costs twice — the company loses its best practitioner and gains a poor manager.