Mileage Log Requirements the IRS Actually Enforces
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Under IRC §274(d) and Temp Reg §1.274-5T, every business mileage deduction requires a contemporaneous log with five specific elements: date, origin, destination, miles, and business purpose. There is no exception, no estimation, and no Cohan rule fallback for vehicle expenses — get audited without a proper log and the entire deduction gets disallowed.
Why Mileage Has Stricter Rules Than Other Deductions
Most business deductions follow the "ordinary and necessary" standard of IRC §162(a). Vehicle expenses are different. Congress designated vehicles as "listed property" under IRC §274(d) because they're frequently used for both personal and business purposes — making them audit targets.
The consequence: for listed property, the Cohan rule doesn't apply. The Cohan rule normally lets taxpayers estimate deductions when records are incomplete. For mileage, if you can't substantiate it with contemporaneous records, the IRS disallows it entirely. No estimates, no approximations.
In case after case, Tax Court has upheld full disallowance of mileage deductions when taxpayers couldn't produce contemporaneous logs. "I drove to my property frequently" is not documentation. The absence of records isn't a gray area — it's an automatic loss under §274(d).
The 5 Required Elements for Every Log Entry
Temp Reg §1.274-5T is the IRS's detailed guidance on what vehicle expense records must contain. For mileage, each trip entry must have all five of the following:
1. Date
The actual date of the trip. "Sometime in March" or "weekly" is not sufficient. Each trip needs its own dated entry. If you make multiple trips in a day, each gets its own entry.
2. Origin
Where you started the trip — your home address, your primary place of business, a client's location, etc. "Home" is acceptable if your address is documented elsewhere. A street address is best.
3. Destination
The address or name of where you drove to. "Home Depot on Main St" or the full address of your STR property. "The property" with no address is weak documentation.
4. Miles Driven
The actual mileage for the trip. Odometer readings at start and end are ideal. GPS-calculated distances from a mileage app also satisfy this requirement. You must record miles, not just distance in general terms.
5. Business Purpose
The specific business reason for the trip. This is where most hosts fall short. "STR" or "rental property" is not enough. "Inspecting property after guest reported broken garbage disposal" or "supply run — purchased cleaning supplies and toiletries for upcoming guest arrival" are the level of specificity the IRS expects.
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What "Contemporaneous" Actually Means
The regulation says records must be made "at or near the time" of the expense. The IRS interprets this as same-day or within a few days at most. Waiting until the end of the month is risky. Waiting until tax season is almost certainly disqualifying.
"Contemporaneous" does not mean handwritten. A mileage app that captures GPS data in real time is contemporaneous by definition — the timestamp proves when the record was made. A spreadsheet you update within a day or two of each trip is also acceptable. A calendar entry made on the day of travel works. What doesn't work: reconstructing trips from memory in December or January.
Use a GPS mileage app (MileIQ, Everlance, or similar) that auto-captures trips. Then spend 10 seconds after each STR-related trip to classify it as business and add a one-line purpose note. That 10 seconds per trip is the difference between a $1,500 deduction and $0.
Acceptable Log Formats
The IRS does not require a specific format. Any of the following work, provided they capture all five required elements:
- GPS mileage tracking app (strongest — timestamped, GPS-verified, hard to dispute)
- Spreadsheet with columns for each required element, updated contemporaneously
- Written log book kept in your vehicle glove box
- Calendar entries with origin, destination, miles, and purpose in the notes field
- Expense tracking software with mileage functionality
Bank statements and receipts alone do not satisfy mileage log requirements. They prove you were at a location but not how far you drove to get there. For more on what records survive a real audit, see our complete Airbnb tax deductions guide and the STR deductions checklist.
Annual Odometer Records
In addition to per-trip records, Temp Reg §1.274-5T requires that you document your vehicle's total mileage for the year (to calculate your business-use percentage). Record your odometer reading on January 1 and December 31 each year. Some hosts photograph their dashboard on those dates for an additional layer of evidence.
Total business miles ÷ total annual miles = business-use percentage. You need this number for Schedule C Part IV (if claiming actual expenses) and it's useful corroboration even if you use the standard mileage rate. Photograph your odometer on January 1 every year.
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Disclaimer
This article is for informational purposes and does not constitute tax, legal, or financial advice. Tax rules vary based on your specific situation, filing status, entity structure, and jurisdiction. Always consult a qualified CPA or tax professional for guidance on your specific tax situation. IRS rules and thresholds are subject to change — verify current requirements at irs.gov before filing.