/company/{id}/position/{id}/candidate/{id}/questionnaire/{id}

Submits a candidate's answers to a questionnaire that was sent to them, validates them against the questionnaire's questions, and marks the questionnaire completed.

Note: questionnaireId is the ID of the candidate's specific questionnaire response (as returned by the list-questionnaires endpoint), not the questionnaire template ID. Each entry in responses is matched to a question by _id: checkbox questions use a responses array of the selected option text values, while all other question types use a single response value. Required questions must be answered, and multiple-choice/dropdown answers must match one of the question's defined options — otherwise the request fails with a 400. Submitting to a questionnaire that is already completed also returns a 400. On success the endpoint returns 204 with no response body.