Google Maps Timeline records where you have been, but it is not a sufficient mileage log for tax purposes on its own. The IRS requires four pieces of information per business mile, and Timeline only captures two of them.
What Timeline records
Google Timeline (now stored on-device only after Google's 2024 changes) records visit places, transit modes, and dates. It does NOT record business purpose or distinguish business from personal trips.
What the IRS requires
A complete mileage log must include date, destination, business purpose, and miles for every business mile. Timeline gives you date and destination. Business purpose and miles must be added separately.
Why this matters
In an audit, "I used Google Maps Timeline" is not a substitute for a mileage log. The IRS may accept Timeline as supporting evidence (corroborating a trip happened) but expects a contemporaneous log with the four required fields.
Could Timeline serve as the basis for reconstruction?
Yes. If you did not track contemporaneously, Timeline can be the source data for a reconstruction. You go through Timeline trip by trip, classify each as business or personal, add a business purpose, and calculate miles. See the reconstruction guide. But this defeats the time savings. You might as well have used a tracker.
What to use instead
A purpose-built mileage app records each trip the moment it happens with all four required fields. The contemporaneous-by-construction property is what holds up best in audits.
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