Mileage for two self-employed businesses: one vehicle, separate purposes

General US federal recordkeeping information, not individual tax advice. Tax treatment depends on your circumstances; consult a qualified adviser for your claim.

Ask your preparer how the activities and expenses should be reported. This guide covers the record structure; it does not decide whether your activities constitute separate businesses or which return schedules apply.

Use purpose codes that remain understandable

Choose short, stable prefixes such as DESIGN and REPAIR. Include the code with a useful description: “DESIGN — deliver approved print proof, project D-18” tells a reviewer more than “Business A.” Keep a private index explaining the codes and their supporting invoices or appointments.

Use a separate category for personal use and another for unresolved allocation. Do not force an uncertain shared journey into a business subtotal solely to finish the spreadsheet. Resolve it with the facts still available.

A fictional vehicle reconciliation

Lena uses one car for design work and an appliance-repair business. Her month-end worksheet reads:

Category	Miles	Treatment in the worksheet
Design-only journeys	184	Assigned once to DESIGN
Repair-only journeys	226	Assigned once to REPAIR
Shared or uncertain journey	30	Held for allocation review
Personal and commuting	260	Excluded from business schedules
All recorded travel	700	Control total

If review supports allocating the 30-mile journey as 12 miles to design and 18 to repair, the resulting business schedules show 196 and 244 miles. Together they total 440. Adding 260 other miles returns the 700-mile control total. The example illustrates arithmetic only; the reason for allocating 12 and 18 must come from evidence, not a desire to split the cost conveniently.

Do not assign the complete 30 miles to both businesses. That would produce 470 claimed business miles for only 440 miles of the reviewed business travel.

Keep the allocation outside unsupported app features

FlatMile's report CSV includes purpose, classification, vehicle and journey information through its report and archive formats. It does not provide a promised dedicated two-business tax-return workflow. A business-purpose prefix can help you review exported rows in a separate worksheet; inspect the file before assuming it contains every field needed for your accounting process.

All FlatMile app CSV and PDF exports require an active subscription or eligible trial. The website's free mileage template is another place to maintain the allocation schedule. Preserve the original exported file and do the allocation work in a copy.

Reconcile expenses as well as distances

If both activities use the same car, send the preparer one vehicle-cost file with the allocation schedules. Two folders containing the same insurance or lease invoice can lead to duplicate expense entries. Mark shared documents clearly and explain how the preparer can trace them to the common vehicle record.

At year end, check that every business-specific distance belongs to the same reporting period and uses the same unit. Include the unresolved items list even if it is empty. Keep prior-year method information with the vehicle rather than independently choosing a different treatment for each activity without review.

The accountant handoff guide is the next step: send a clear index, the unaltered vehicle record and the reviewed allocation schedules together.