detailed written report; formal incident report
A formal business document that explains the circumstances, causes, and actions taken in response to a problem or incident. Often required in Japanese corporate settings.
Because a problem occurred, I was asked to submit a formal incident report.
In a formal incident report, you must write the cause and countermeasures in detail.
報告書 is a general report, not necessarily incident-related. 顛末書 is specifically a report on the full story of a particular incident or problem.
顛末 (てんまつ) means 'the full story' or 'circumstances from beginning to end', and 書 (しょ) means 'document'. The compound refers to a document detailing the complete account of an incident.