When this guide is useful
An owner has vehicle expenses but incomplete contemporaneous trip records.
The distinction that matters
A calendar can help identify trips but does not automatically establish deductible mileage. Separate supported business travel, commuting and personal use before selecting a reporting method.
A worked situation to investigate
A home-service owner remembers several jobs but the odometer readings and appointment locations do not yet agree.
The example is illustrative. Begin with the underlying event and its source documents, then separate missing facts from disagreements about their treatment. Work through the checks below in the order that matches your file, rather than treating a completed checklist as a tax conclusion.
Build a traceable handoff
Identify the affected person, entity or property and the relevant period. Keep original evidence, corrections and the reviewer's written conclusion connected. If the facts change after review, preserve the earlier version and ask whether the change affects implementation.