Personal vs. Business Use: How Does the IRS Draw the Line on Vehicle Expenses?

When you use a vehicle for both work and personal purposes, only the business portion of your expenses is potentially deductible. The IRS applies the "ordinary and necessary" standard under §162 of the Internal Revenue Code, which means a deductible expense must be common in your trade or business and helpful for carrying it out. Commuting from home to a regular workplace is treated as personal use, not business use, regardless of how far you travel. Keeping accurate records is essential, because the IRS requires contemporaneous documentation to support any vehicle deduction you claim.

The Core Rule: §162 and "Ordinary and Necessary"

Business deductions for vehicle expenses flow from Internal Revenue Code §162, which allows a deduction for ordinary and necessary expenses paid or incurred in carrying on a trade or business. For a vehicle expense to qualify:

Ordinary — the expense is common and accepted in your type of business.
Necessary — the expense is helpful and appropriate for your business (it does not have to be indispensable).

Both conditions must be met. A vehicle used solely to drive to a single fixed office every day generally fails this test for the commuting miles, even if the vehicle is otherwise used for legitimate business purposes.

Business Use vs. Personal Use: Key Distinctions

The IRS draws the line by looking at the purpose of each trip, not the type of vehicle or who owns it.

Business use generally includes: traveling between job sites, visiting clients or customers, driving to a temporary work location, and travel required by your employer that is not reimbursed.
Personal use generally includes: commuting between your home and a regular place of business, running personal errands, and any travel for non-work reasons.
Commuting rule: The IRS consistently treats home-to-office commuting as a personal expense. Distance alone does not convert a commute into a deductible business trip.

Mixed-Use Vehicles

Most people who claim vehicle deductions use the same car or truck for both business and personal purposes. This is called a mixed-use vehicle. In that situation, only the business-use percentage of total miles driven during the year is deductible.

For example, if you drive 15,000 miles in a year and 9,000 of those miles are documented business miles, your business-use percentage is 60%. You may only apply that 60% figure when calculating your deduction, whether you use the standard mileage rate or actual expenses.

Two Methods for Calculating the Deduction

Taxpayers generally choose between two IRS-approved methods:

Standard mileage rate — Multiply your documented business miles by the IRS rate for that tax year. This rate is updated periodically and is published in IRS guidance each year.
Actual expense method — Deduct the business-use percentage of your real costs: gas, oil, repairs, insurance, registration fees, depreciation, and similar expenses.

There are rules about which method you may use and whether you can switch between them. Consulting a tax professional before choosing a method is advisable, especially in the first year you place a vehicle in service.

Why Recordkeeping Matters

The IRS requires contemporaneous records, meaning records made at or near the time of each trip, to substantiate vehicle deductions. A compliant mileage log typically includes:

The date of each trip
The destination and business purpose
The number of miles driven
The total odometer reading at the start and end of the year

Without adequate records, a deduction can be disallowed entirely upon audit, even if the underlying business travel genuinely occurred.

Does it matter whether the vehicle is owned by me personally or by my business?

Ownership affects how the deduction is reported and may affect which expenses are deductible, but the fundamental §162 "ordinary and necessary" standard applies in both cases. A vehicle titled in your personal name that you use for business can still generate a deduction; likewise, a company-owned vehicle used for personal trips creates a taxable fringe benefit for the employee or owner. The business-use percentage must still be calculated and documented regardless of how title is held.

Is my commute ever deductible?

In most situations, no. The IRS treats travel between your home and a regular, fixed place of business as a personal commute. There are narrow exceptions. For example, travel from home to a temporary work location may be deductible if you already have a regular place of business elsewhere. The home-office rules also interact with commuting in specific ways. Because these exceptions are fact-specific, a tax professional can help you determine whether your particular situation qualifies.

What is a "temporary" work location?

The IRS generally considers a work location temporary if employment there is expected to last (and does in fact last) one year or less. If you realistically expect an assignment to exceed one year, the location is treated as indefinite rather than temporary, and travel from home to that location is treated as a non-deductible commute. The one-year rule is applied based on your reasonable expectation at the time the assignment begins.