What a certificate of completion does and does not prove

A certificate of completion says a person worked through the material and passed the assessments in it. That is worth having and it is not the same as competence, because the assessment was not invigilated and it did not watch anyone do the task. We are direct about this with our own online certificates, which record completion rather than assessed competence. Where the distinction matters — a client pre-qualification, a regulator, an insurer — how do you evidence the gap between the two, and what have you been asked for?