Mileage guide
How to Keep Business Mileage Records for Two Vehicles
By FlatMile ·
General US federal recordkeeping information, not individual tax advice. Tax treatment depends on your circumstances; consult a qualified adviser for your claim.
At a glance
Keep separate mileage records for each vehicle, then create a combined summary only after each vehicle reconciles on its own. Every journey should belong to the car actually driven. A household mileage total cannot tell you how one vehicle was used or which expenses belong to it.
This guide is an organizing workflow, not a claim about automatic vehicle recognition or multi-vehicle reporting in a particular app. You can use separate worksheets, clearly identified files or another system that preserves the vehicle distinction.
Give each vehicle a stable identity
Use a label that will remain clear next year, such as “Blue hatchback” and “White van,” plus a private reference sufficient to distinguish them. Avoid ambiguous names such as “my car” if the vehicle changes during the year.
Create a cover row for each vehicle with the reporting period, opening and closing odometer evidence, distance unit and dates it was available for business use. Keep repair and other vehicle-specific documents with the corresponding record rather than in an undifferentiated folder.
When another person drives the vehicle, your own business-trip log may not describe all its use. Reconcile against the vehicle's total movement, not just the journeys your phone happened to record.
Work through each vehicle first
The following fictional full-year example assumes the readings and categories have already been verified. It illustrates arithmetic, not a deduction calculation.
| Vehicle | Opening odometer | Closing odometer | Total miles | Business miles | Business share |
|---|---|---|---|---|---|
| Blue hatchback | 24,000 | 34,000 | 10,000 | 3,000 | 30% |
| White van | 8,000 | 14,000 | 6,000 | 4,800 | 80% |
| Combined summary | Not applicable | Not applicable | 16,000 | 7,800 | 48.75% |
The combined share is 7,800 divided by 16,000. It is not the simple average of 30% and 80%, which would be 55%. More importantly, the combined percentage must not replace the vehicle-specific calculation when allocating that vehicle's expenses.
IRS Topic 510 explains allocating costs between business and personal use. Method eligibility and the treatment of each vehicle need their own review; use standard mileage versus actual expenses to prepare that discussion.
Catch vehicle mix-ups at the journey level
Imagine a supplier visit recorded in the hatchback's worksheet on a day you borrowed the van. Correct the vehicle assignment and keep a brief explanation. Do not leave it in one file and add a copy to the other.
Review dates when you switched cars, shared a car with a partner or used a replacement vehicle. Check overlapping journey times: two records for different vehicles may be legitimate drivers, or they may reveal an assignment error. Investigate the facts before deleting either.
Prepare a clear year-end handoff
Provide one summary per vehicle and a separate combined overview if useful. Include unresolved questions such as a missing opening reading or an uncertain vehicle assignment. Do not fill an odometer gap by borrowing the other car's reading.
If you replaced a vehicle, preserve the cutoff date and separate acquisition/disposal paperwork for your adviser. If you simply used two cars throughout the year, maintain both logs through the closing date. The year-end checklist helps finish the records, and the accountant package guide explains how to present them without obscuring open issues.