If you have unreimbursed vehicle expenses as an employee (not commuting) you claim them on IRS form 2106. It's an itemized deduction on your income taxes but has to exceed 2% of your Adjusted Gross Income.
If your employer permits, you can keep your company car at home. However, any non-business use, such as commuting to and from work or using the car on weekends, is personal use, and the value of this use of the vehicle will be taxed.
Report the value of personal use of a company vehicle on Form 941 and the employee's Form W-2.
In short, yes the employer can. In California all employment is considered to be on an at will basis unless there is an agreement to the contrary about that status between the employee and employer.
Examples of driving a company vehicle for personal use include: Your employee's commute between home and work, if it is on a regular basis. Trips unrelated to your organization's purpose, work, trade, etc. Use on a vacation or on the weekend.
To find an employee's PUCC value under the cents-per-mile rule, multiply their personal miles driven by the IRS standard mileage rate. For 2025, the standard mileage rate is 70 cents per business mile drive. The rate includes the costs of maintenance, insurance, and fuel.
Therefore your employer will withhold federal income taxes, Medicare taxes, and Social Security taxes from your paycheck based on the value of your personal use of the company car. Any use of the company car for any non-business purposes is considered to be personal use.
A personal vehicle is primarily used for the private purposes of its owner or someone authorized by the owner. This differs from a business vehicle, a car for hire, and a commercial vehicle.
You can deduct the car expenses as a business expense. If you also use the car for personal use, the value of the personal use has to be added to your W-2 box 1 taxable income because it is a taxable employee benefit. This is still messy, though slightly less messy than leasing the car to yourself.
In short, yes the employer can. In California all employment is considered to be on an at will basis unless there is an agreement to the contrary about that status between the employee and employer.