Mileage Log Guide: What to Include, How to Write One, and Common Mistakes

If you use a vehicle for business, the IRS expects you to track your mileage. A proper mileage log does one thing: it separates business miles from personal miles so you can claim the correct deduction. Without it, you leave money on the table or invite an audit. Here’s exactly what to track, how to do it, and the mistakes that trip up most business owners.

What to Include in a Mileage Log

The IRS requires four fields for every business trip. Miss one, and that trip may not count during an audit.

• Date of the trip
• Starting and ending odometer readings (or total miles driven that trip)
• Destination – the full address or at minimum the city and state
• Business purpose – a one-line explanation like "client meeting at 123 Main St" or "supply run to Home Depot"

A fifth field — total miles — is smart to add. That way you can quickly tally business vs. personal use without doing math on every entry.

Here’s a real example: On March 12, you drive from your home office at 45 Maple Ave to a client site at 789 Oak Dr. Your odometer reads 32,450 at start and 32,478 at end. Business purpose: "Deliver project proposal and collect signed contract." That’s 28 business miles, logged.

How to Write a Mileage Log Step by Step

You have two options: paper or digital. Paper works fine if you’re disciplined. Digital apps (like MileIQ, Everlance, or QuickBooks’ built-in tracker) automate the process and reduce errors.

Step 1: Record each business trip as you go. Don’t wait until year-end. The IRS requires "timely" records — meaning within a week of the trip.

Step 2: Pick one deduction method for the year. You can use the Standard Mileage Rate (67 cents per mile for 2024) or Actual Expenses (gas, repairs, insurance, depreciation). You cannot switch mid-year. Your log feeds whichever method you choose.

Step 3: Separate personal trips. Log them too. A log with only business trips looks suspicious. Personal entries with zero business purpose create a complete picture.

Step 4: Total your business miles at year-end. Multiply by the current IRS rate if using the Standard Mileage Rate, or calculate the business-use percentage for Actual Expenses.

Common Mistakes That Trigger IRS Scrutiny

Mistake #1: Backdating entries. The IRS looks for patterns. A log written in December that covers the whole year with neat handwriting is a red flag. Real logs have coffee stains, skipped days, and varying ink colors.

Mistake #2: Using the same destination every time. If you drive to the same client every Tuesday, log each trip separately. A recurring weekly entry with no date variation looks fabricated.

Mistake #3: Forgetting the business purpose. "Meeting" is too vague. Write "Quarterly review with ABC Corp" or "Deliver equipment to job site 42." Specificity protects you.

Mistake #4: Mixing commuting miles. Your commute from home to your regular office is personal, not business. Trips from your office to a client site are business. Many owners wrongly deduct the commute.

Mistake #5: Not logging personal trips. If you claim 90% business use but have no personal trips recorded, an auditor will assume the gap was personal. Your deduction shrinks.

Paper vs. Digital: Which Works for You?

Paper logs are free, simple, and meet IRS requirements. Download the IRS’s own template (Form 4562 instructions include one). Keep it in your glove box.

Digital logs save time and reduce errors. Most apps let you swipe to classify a trip as business or personal. They also export reports your accountant can use directly.

Either works. The key is consistency. A perfect digital log you never open is worse than a messy paper log you update weekly.

What About Employees?

If you reimburse employees for vehicle expenses, you need their mileage logs too. Without them, the IRS may treat reimbursements as taxable wages. You can require employees to submit monthly logs and reimburse at the standard rate. Keep those logs with your business records for at least three years.

A solid mileage log takes five minutes per week. That five minutes could save you thousands in deductions and hours of audit stress.