🚗 2025 Mileage Log Requirements — What the IRS Actually Accepts (and Rejects)
Your car deduction depends on one thing more than any other: the quality of your mileage log. The IRS doesn’t require fancy apps or spreadsheets — just clear, consistent, real-time records.
1️⃣ Required Elements of an IRS-Compliant Mileage Log
Mileage logs must show a clear business purpose and reflect real driving patterns.
The IRS routinely checks for the following five elements:
- Date of each trip
- Starting and ending locations
- Business purpose written in plain English
- Miles driven for each segment
- Annual odometer readings (January 1 & December 31)
“Client meeting” is too vague for the IRS.
A better description: “Consultation with Client B regarding contract revision.” Specificity increases credibility.
2️⃣ Sample Daily Entries — Audit-Proof Format
Here’s a clean, realistic example of what a same-day log might look like.(Brand-new example — not used in any previous post.)
• Home → Warehouse District
• Purpose: Inventory inspection for Project Delta
• Mileage: 14.7 miles
• Warehouse → Client Office (Downtown)
• Purpose: Presentation delivery + review session
• Mileage: 6.9 miles
• Client Office → Supplier Hub
• Purpose: Pick up replacement parts
• Mileage: 8.3 miles
👉 Total business mileage: 29.9 miles
If your day includes both business and personal trips, enter them separately rather than combining segments. Mixed entries are a common audit problem.
3️⃣ Monthly & Annual Tracking Best Practices
Mileage logs are easiest to maintain when organized monthly. This also helps identify unusual patterns before tax season.
- Create one sheet per month with automatic totals
- Record recurring destinations (clients, vendors) as presets
- Match your mileage log with calendar events
- Separate family errands even if they occur mid-route
- Review monthly totals to ensure consistency with your occupation
• Business miles: 540 miles
• Total miles: 1,005 miles
• Business-Use Percentage: 540 ÷ 1,005 = 53.7%
• Active workdays with driving: 17
• Fuel + maintenance costs: $602
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4️⃣ Patterns the IRS Flags as Red Flags
The IRS rarely disallows mileage because of “one mistake.”
Instead, they look for patterns that suggest estimates or reconstructed logs.
- Rounded numbers (10, 20, 30 miles repeatedly)
- Same mileage every Monday–Friday
- Logs created only at year-end
- Trips with vague business purposes
- Total annual miles inconsistent with car age or occupation
The strongest logs are those that match your digital calendar. IRS agents frequently compare meeting times with mileage entries.
5️⃣ FAQ for Real-Life Scenarios
Q1. Do I need to record round-trip mileage?
→ No. Record each segment separately — it creates a clearer audit trail.
Q2. Is a mileage app better than a spreadsheet?
→ Either works. What matters is consistency and accurate business purpose descriptions.
Q3. What if a business trip includes a personal detour?
→ Log the business portion only. Personal segments must be excluded.
🔗 EA Tax Guide Internal Links
Reference Links
This post summarizes U.S. federal tax rules.
State rules for registration fees, personal property tax, and documentation requirements may differ. Always check your state’s specific guidance.
- Part 1 — 2025 Car Expense Deduction Guide
- Part 2 — Business-Use % for Mixed-Use Vehicles
- Part 3 — 12 Actual-Method Car Expenses You Can Deduct
- Part 4 — Mileage Log Requirements & Best Practices
- Part 5 — Depreciation, Section 179 & Bonus Depreciation
- Part 6 — Deductible Travel Expenses
- Part 7 — Mixed Family + Business Trips
- Part 8 — How the 50% Meals Deduction Works
- Part 9 — Home Office Deduction Methods
- Part 10 — Form 8829 Calculation Example