The IRS does not require a specific mileage log format. A paper log book, a spreadsheet, or an auto-tracking app are all acceptable. The right choice depends on your driving volume and your discipline at logging.
Paper log book
How it works: a notebook in your glove box. One row per trip with date, destination, business purpose, miles. Pen and paper, simple.
Pros: cheapest. No technology. Always available. Hand-written entries are inherently contemporaneous if you fill them at trip's end.
Cons: slow to fill out per trip. Easy to forget when you are tired. Easy to lose. Hard to total at year end. Hard to share with a tax preparer.
Best for: drivers with under 5 business trips per week who are disciplined about logging.
Spreadsheet
How it works: Excel or Google Sheets template. One row per trip, columns for date / destination / purpose / miles. Auto-totals at the bottom.
Pros: fast totaling. Easy to share with accountant. Backups via cloud sync.
Cons: still requires you to enter every trip. Most people forget within days, then catch up retroactively (which fails the contemporaneous test). Format detail varies wildly by template; many templates miss the four required IRS fields.
Best for: drivers with moderate volume (5-15 business trips a week) who use a phone-friendly spreadsheet app and log within a day or two of each trip.
Mileage tracking app
How it works: auto-detection runs in the background. Each trip is timestamped at the moment it starts and ends. You classify (one tap) and add business purpose at end of day or week.
Pros: contemporaneous by construction. Catches trips you would have forgotten. One-tap year-end export. The four required IRS fields are automatic.
Cons: requires location permission and battery awareness. Free tiers cap monthly trip count.
Best for: drivers with high volume (gig drivers, multi-stop trades, sales reps) and anyone who has ever forgotten to log a trip.
What the IRS prefers
The IRS does not prefer one format over another. They prefer COMPLETE and CONTEMPORANEOUS. A clean app log beats a clean paper log only because the contemporaneous-by-construction property is automatic. A poorly maintained spreadsheet loses against a well-maintained paper log.
Switching between formats
Most apps export to CSV, which can be imported into a spreadsheet or shared with a tax preparer. Going the other direction is harder. Manually entered spreadsheet rows do not become app entries automatically. Pick one format and stick with it for a tax year.
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