Business Use of a Personal Vehicle: How to Split Expenses and Maximize the Deduction

By Yarik Yarosh, CPA ·September 5, 2026 ·5 min read

Written by Yarik Yarosh, CPA (US & Canada) September 5, 2026 · FL CPA license AC61704 · CPA Ontario

Most small business owners use their personal vehicle for both business and personal purposes. The IRS allows a deduction only for the business portion, and the business owner must choose between two methods: the standard mileage rate (70 cents per mile for 2025) or actual expenses (with depreciation) prorated by the business-use percentage. Under IRC 274(d), vehicles are “listed property” subject to strict substantiation requirements, meaning the IRS can deny the entire deduction if the taxpayer can’t produce a contemporaneous mileage log. Unlike most other business expenses, the Cohan rule (estimating expenses when records are incomplete) doesn’t apply to vehicles. Without a mileage log, the deduction is $0, regardless of how many business miles were actually driven.

✓Key takeaway

Standard mileage rate vs. actual expenses:

Factor	Standard Mileage Rate	Actual Expenses
2025 rate	70 cents/mile	N/A (track all costs)
Record-keeping	Mileage log only	Mileage log + all expense receipts
Includes	Gas, insurance, depreciation, repairs, tires, registration	Each expense tracked separately
Doesn’t include	Tolls, parking (deductible separately)	N/A (all costs included)
Best for	Lower-cost vehicles, high mileage	Expensive vehicles, high actual costs
Switching rules	Must elect in first year of business use. Can switch TO actual later.	Can switch to standard only if you used standard first AND never claimed depreciation.

What counts as business miles:

Business Miles (Deductible)	NOT Business Miles
Driving to client meetings	Commuting (home to office)
Driving between business locations	Personal errands
Driving to the bank for business	Driving to/from lunch (unless with a client for business)
Driving to pick up business supplies	Side trips for personal purposes
Driving to a temporary work location	Driving from home to regular office (commuting)

The home office exception: If the taxpayer has a qualifying home office, their home IS their principal place of business. Drives from home to any business location are business miles, not commuting.

Scenario	Without Home Office	With Home Office
Home to client meeting	Commuting (not deductible)	Business miles (deductible)
Home to office supply store	Personal	Business miles (deductible)
Home to second office	Commuting	Business miles (deductible)

The home office converts what would be commuting miles into business miles. For a taxpayer who drives 15,000 “commuting” miles per year, the home office deduction alone creates $10,500 in vehicle deductions (15,000 x $0.70).

How do the two methods compare?

Hypothetical example

Round numbers. A sole proprietor. Drives a 2022 Toyota Camry (original cost $28,000). Total miles: 20,000 per year. Business miles: 12,000. Personal miles: 8,000. Business-use percentage: 60%.

Method 1: Standard mileage rate

Item	Calculation	Deduction
Business miles x rate	12,000 x $0.70	$8,400
Tolls (business trips)		$200
Parking (business meetings)		$300
Total deduction		$8,900

Method 2: Actual expenses

Expense	Total Annual Cost	Business % (60%)	Deduction
Gas	$3,000	$1,800	$1,800
Insurance	$1,800	$1,080	$1,080
Repairs/maintenance	$1,200	$720	$720
Tires	$600	$360	$360
Registration	$200	$120	$120
Car wash	$240	$144	$144
Depreciation (MACRS 5-year)	$5,600 (Year 1)	$3,360	$3,360
Tolls	$200	(full, not prorated)	$200
Parking	$300	(full, not prorated)	$300
Total deduction			$8,084

Comparison:

Method	Total Deduction
Standard mileage rate	$8,900
Actual expenses	$8,084
Winner	Standard mileage rate by $816

The standard mileage rate wins for this mid-range vehicle with moderate costs. Actual expenses tend to win for:

Expensive vehicles with high depreciation
Vehicles with significant repair costs
Vehicles with high insurance premiums
Low-mileage business use (few miles but expensive per-mile costs)

When actual expenses win (luxury vehicle example): A business owner drives a 2025 BMW X5 (cost $65,000, over 6,000 lbs GVWR).

Method	Deduction
Standard mileage (12,000 x $0.70)	$8,400
Actual expenses (60% of $12,000 costs + $18,720 depreciation at 60%)	$11,232 + $1,800 = $13,032

For expensive vehicles, actual expenses produce a larger deduction because the depreciation component is significant.

The mileage log requirement: Every entry must include:

Element	Example
Date	March 15, 2025
Starting odometer	45,230
Ending odometer	45,258
Miles	28
Destination	ABC Corp, 123 Main St
Business purpose	Client meeting to discuss Q2 project

The log must be contemporaneous (recorded at or near the time of the trip). Apps like MileIQ, Everlance, and TripLog automate this with GPS tracking. A spreadsheet updated weekly is also acceptable. A reconstruction of mileage at year-end isn’t sufficient and will be denied on audit.

What happens without a mileage log:

Scenario	IRS Position
No mileage log at all	Entire vehicle deduction denied ($0)
Partial log (some months missing)	Only documented months allowed
Estimated mileage (no log)	Denied (Cohan rule doesn’t apply to vehicles)
Credit card statements showing gas purchases	Not sufficient alone (proves cost, not business purpose)
Calendar showing client meetings	Helpful but not sufficient without miles

Tax savings summary:

Income Level	Deduction ($8,900)	Tax Savings
$50,000 (22% bracket)	$8,900	$1,958
$100,000 (24% bracket)	$8,900	$2,136
$150,000 (32% bracket)	$8,900	$2,848
$200,000 (32% bracket)	$8,900	$2,848

Plus SE tax savings: $8,900 x 15.3% x 92.35% = $1,258 (if sole prop). Total savings at the 32% bracket: $4,106 per year.

Illustrative numbers only, not a real client and not advice for your facts.

Want this checked against your own situation?

Start with a Diagnostic: a CPA licensed in the US and Canada reads your file and answers in writing, three to four business days after you finish the questions. $250 for cross-border, $195 for a second opinion on a filed return, and it comes straight off the bill if we do the work after. Or book a free 15-minute fit call first.

Start a Diagnostic →Book a free call

Get the next cross-border guide by email

One or two plain-English guides a week on US-Canada tax. No spam, unsubscribe anytime.

Cite this page

Yarik Yarosh, CPA. "Business Use of a Personal Vehicle: How to Split Expenses and Maximize the Deduction." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/small-business-tax-deduction-business-use-personal-vehicle

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.