FMCSA §396.11 is the regulation that requires a written Driver Vehicle Inspection Report (DVIR). Here is what it actually says, in plain English.
The text
Every motor carrier shall require its drivers to report, and every driver shall prepare a report in writing at the completion of each day’s work on each vehicle operated...
What it means in practice
At the end of every driving day, the driver must complete and sign a written report covering: brakes, parking brake, steering, lighting and reflectors, tires, horn, wipers, mirrors, coupling devices, wheels/rims, and emergency equipment.
Defect retention
If defects are noted, the carrier signs confirming repair OR confirming defects do not affect safe operation, before the vehicle is next dispatched. The report is then retained for three months.
If no defects?
No retention required beyond the next inspection. But you still have to complete the form — not completing it is itself a violation.