If you repair or perform service on an aircraft, you are responsible for making a record of that work. Depending upon whether you are the aircraft owner or a mechanic, those records could include logbook entries, work cards, estimates, work orders and invoices. Unfortunately, if those records are not prepared carefully, and as required by the FARs, the person making the record could be exposing himself or herself to FAA enforcement action or civil liability.
For a more detailed discussion of this issue, please read my article on the topic here. Or, if you still have questions on the subject after reading the article, feel free to call.