Yes, you need odometer readings for taxes if you plan to claim any vehicle deduction. The IRS requires three numbers each year (your odometer on January 1, your odometer on December 31, and your total business miles built from a trip-by-trip log) and this applies whether you use the standard mileage rate or deduct actual vehicle expenses. Without those readings tied to a contemporaneous log, the deduction is gone.
Why the IRS Requires Odometer Readings
The rule comes from Internal Revenue Code Section 274(d), which blocks any deduction for listed property (vehicles included) unless you document the amount, the time and place of use, and the business purpose behind each trip.1Office of the Law Revision Counsel. 26 U.S. Code 274 – Disallowance of Certain Entertainment, Etc., Expenses The burden sits entirely on you. The IRS does not have to prove your driving was personal; you have to prove it was business.
This is stricter than most parts of the tax code. For a typical expense, if your records are thin but a court believes the spending happened, it can estimate a reasonable amount. Vehicles don’t get that fallback. Section 274(d) demands strict substantiation, and incomplete records mean the whole deduction is disallowed, even when no one disputes that you actually drove for work.
The Three Odometer Numbers You Need Every Year
No matter which deduction method you pick, three readings anchor the return:
- Your odometer on January 1, which sets the baseline for the year.
- Your odometer on December 31. Subtract the January 1 reading and you have total annual miles.
- Your total business miles, added up from the individual trip entries in your log.
Business miles divided by total annual miles gives your business-use percentage. That single fraction drives the standard mileage deduction, the share of actual expenses you can write off, and any depreciation you claim. An error in either number ripples through everything else on the return.
What Each Trip Entry Must Show
A compliant mileage log records four things for every business trip: the date, the destination, the business purpose, and the starting and ending odometer readings for that trip.1Office of the Law Revision Counsel. 26 U.S. Code 274 – Disallowance of Certain Entertainment, Etc., Expenses Daily totals alone are not enough. The log has to tie specific miles to specific business reasons, and that link is where most deductions fall apart in an audit.
The record must also be contemporaneous, meaning made at or near the time of the trip. A spreadsheet built in March from memory of last year’s driving is exactly the kind of reconstruction the IRS rejects. Smartphone apps and GPS-based trackers meet the standard well because they timestamp and geolocate each trip, but you still have to note the business purpose yourself. An app that logs 14.3 miles to a downtown address on a Tuesday afternoon proves nothing without a note saying you met a client there.
Consistency matters too. A log that carefully tracks January through April, goes blank until November, then picks up again will weaken the months that were done properly.
Which Trips Count as Business Miles
Your log needs to separate three kinds of driving, and only one is deductible. Business miles count. Commuting between your home and your regular workplace does not. Personal driving, obviously, does not either.2eCFR. 26 CFR 1.274-14 – Disallowance of Deductions for Certain Transportation and Commuting Benefit Expenditures Examiners cross-check claimed business miles against total annual miles, so inflating one while ignoring the other is a common flag.
Business mileage includes driving between two work locations, visiting a client, going to a business meeting, or traveling to a temporary work assignment expected to last one year or less.3Internal Revenue Service. Topic No. 511, Business Travel Expenses Once a temporary assignment is expected to run longer than a year, that same travel becomes nondeductible commuting.
The Home Office Wrinkle
If you have a qualifying home office that serves as your principal place of business, driving from home to any other work location in the same business counts as business travel, not commuting.4Internal Revenue Service. Publication 587 – Business Use of Your Home For self-employed people working mainly from home, that turns the first and last trips of the day into deductible mileage instead of a nondeductible commute.
How Your Readings Turn Into a Deduction
Your odometer data feeds one of two methods. Pick whichever produces the larger write-off, but note that the choice you make in the first year the car goes into business service affects your options later.
Standard Mileage Rate
Multiply business miles by the IRS rate. For 2026, that rate is 72.5 cents per mile.5Internal Revenue Service. 2026 Standard Mileage Rates You report it on Schedule C if you’re self-employed, or Form 2106 if you’re a qualifying employee such as an Armed Forces reservist or fee-basis government official. You don’t track fuel, insurance, or repair costs separately, but you still need the annual mileage numbers. Parking fees and tolls tied to business travel are deductible on top of the standard rate, so hold onto those receipts.6Internal Revenue Service. Topic No. 510, Business Use of Car
Actual Expense Method
Here you total every vehicle-related cost for the year (fuel, oil, repairs, tires, insurance, registration, depreciation) and multiply that total by your business-use percentage. Parking and tolls for business use are added on separately, same as with the standard rate.6Internal Revenue Service. Topic No. 510, Business Use of Car Actual expenses tend to win when the vehicle is expensive to own relative to how much you drive it. The cost is heavier recordkeeping on top of the mileage log.
Either way, the odometer readings are doing the same work. Under the standard rate they set the mileage you multiply. Under actual expenses they set the percentage you multiply by. You cannot skip them and use either method.
Charitable, Medical, and Military Move Mileage
Business driving isn’t the only kind that needs a log. If you drive for qualifying charitable work, medical appointments, or a military-related move, the same four-item entry applies: date, destination, purpose, and trip-specific odometer readings. The 2026 rates are 20.5 cents per mile for medical purposes, 14 cents per mile for charitable service, and 20.5 cents per mile for qualified moves by active-duty Armed Forces members ordered to a permanent change of station.7Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile, Up 2.5 Cents
Medical mileage is only deductible to the extent total medical expenses top 7.5% of your adjusted gross income, and only if you itemize. Charitable mileage goes on Schedule A as a contribution. Neither category lets you swap in the actual expense method; the fixed rates are the only path.
How Long to Hold the Records
The general rule is three years from the date you filed or from the return’s due date, whichever is later.8Internal Revenue Service. How Long Should I Keep Records Vehicles are listed property, though, and the IRS wants records for as long as depreciation recapture is possible, which stretches across the asset’s full recovery period.9Internal Revenue Service. Publication 946 – How to Depreciate Property For a car depreciated over five years under MACRS, that works out to keeping mileage logs, purchase documents, repair receipts, and insurance records for at least eight years.
Digital copies are fine alongside paper. The IRS accepts electronically stored records as long as the system keeps them accurate and can produce legible copies when asked.
What Happens If You Skip the Log
An examiner who asks for your mileage log and doesn’t get one will disallow the entire vehicle deduction, not just a slice. That raises your taxable income and creates a deficiency. On top of the additional tax, the IRS can add a 20% accuracy-related penalty on the underpayment, plus interest running from the original due date of the return.10Internal Revenue Service. Accuracy-Related Penalty
The numbers add up fast. A self-employed driver claiming 20,000 business miles at the 2026 rate is deducting $14,500. Lose that at a combined federal and self-employment rate above 30% and you owe roughly $4,500 in tax, another $900 in penalties, plus interest. All to avoid keeping a log that costs nothing to maintain.