Company Car Tax Basics Every Founder Should Understand Before Buying
A car used for business brings real deductions and real record-keeping duties, so here is how the main rules work and what to ask your accountant.
A founder who buys a car through the company because it is a business expense often discovers later that the tax treatment depends on details nobody checked: how much it is used for business, who drives it, and what records exist. The rules are not obscure, but they are specific.
This is not a guide to whether you should buy a car through the business. That depends on your entity, your tax position, and how you use the vehicle. It is an explanation of the main mechanisms so you can have a better conversation with your accountant.
The core idea is that only the business portion of a vehicle's costs is deductible. If a car is used partly for business and partly for personal driving, the costs are generally split according to the share of use that is business.
Commuting between home and a regular place of work is generally treated as personal, not business, under IRS rules. Driving between work locations, to meet customers, or on business trips can count as business use. IRS Publication 463 sets out the details, including the treatment of temporary work locations and home offices.
That makes the business-use percentage the number everything else depends on, and it is the number most likely to be challenged if records are thin.
Two ways to calculate the deduction
For vehicles used in business, the IRS generally allows two methods. The standard mileage rate multiplies business miles driven by a rate the IRS sets, which changes over time and can change within a year. The actual expense method adds up real costs, such as fuel, maintenance, insurance, registration, and depreciation or lease payments, and multiplies them by the business-use percentage.
The choice is not always free to change later. Publication 463 explains the restrictions. For a car you own, for example, you generally need to use the standard mileage rate in the first year the car is used for business if you want the option to use it in later years. Check the current rules with your accountant before the first year's return.
Rates and limits change, so look up the current standard mileage rate on the IRS website rather than relying on a figure you remember.
Depreciation has its own limits
If you own the vehicle and use the actual expense method, depreciation is usually a significant part of the deduction. Cars fall into a category the IRS calls listed property, which brings extra rules. In general, a vehicle must be used more than half for qualified business purposes to claim certain accelerated deductions, such as the section 179 deduction and special depreciation allowances.
Passenger automobiles are also subject to annual caps on depreciation, which the IRS adjusts over time. Certain heavier vehicles are treated differently under the rules. Publication 463 and Publication 946 cover how the limits work, and your accountant can tell you which category a particular vehicle falls into.
Employee use creates a fringe benefit
If the company provides a car to an employee, including a founder who is an employee of their own corporation, personal use of that car is generally a taxable fringe benefit. IRS Publication 15-B explains how employers value that personal use, with methods including a cents-per-mile rule, a commuting rule, and a lease value rule, each with conditions.
That value typically needs to be included in the employee's wages. Many founders are surprised by this, because they assumed a company car was simply a company expense. Getting it wrong can mean incorrect payroll reporting.
Records make or break the deduction
The IRS expects adequate records to support vehicle deductions, which generally means a log of business miles, dates, destinations, and purposes, along with records of expenses. A mileage app, a simple spreadsheet, or a notebook in the glovebox can all work, as long as entries are made at or near the time.
Reconstructing a year of driving from memory at tax time is the most common way vehicle deductions become hard to support.
What to do before you buy
Estimate realistically how much of the car's use would be business and how much would be commuting or personal. Ask your accountant which calculation method suits you and what the first-year choice commits you to. Check whether the vehicle is subject to passenger automobile depreciation caps. If the company will provide the car to you or an employee, ask how personal use will be valued and reported through payroll. Set up a mileage log on the first day you drive it.
This is general information, not tax advice. Rates and thresholds change; confirm current figures with the agencies linked below or with your accountant.
Sources
IRS — Publication 463, Travel, Gift, and Car Expenses
IRS — Publication 15-B, Employer's Tax Guide to Fringe Benefits
