The free use of a company car
is one of the best perks an employee may be entitled to as part of a compensation package. But the benefit to the employee isn't completely "Free" under current tax law. Essentailly, personal use of a company car is treated as a taxable fringe benefit, subject to income tax withholding obligations by the employer. This process is often complicated by the complexity of the related tax rules.
Basics about Company-Provided Cars