In general, employees may be compensated for accidents and injuries incurred on the job or in connection with work-related duties. However, the specifics of workers' compensation are not regulated by federal law but rather by state legislation. Even though there are many general similarities, the specifics of each case are individual and should be assessed on a case-by-case basis according to state law.
Employer-Owned Parking Lot
If an employee slips and falls while walking to work through the employer's parking lot, this will very likely be covered by workers' compensation. Similarly, if the employer does not have a parking lot, but maintains some form of control at another parking lot-- such as leasing spaces for employees to use -- or the employer requires employees to park in a nearby lot, that too is likely to be covered.
Parking Lot Outside Employer Control
If an employee parks in the parking lot of a store to do some shopping on her lunch break, this is unlikely to be covered by workers' compensation. It does not constitute a work-related duty, nor did the employer require the employee to park in that lot. However, if the employee is driving to deliver products to that store on behalf of the employer, this would likely be covered, since the employee was required to navigate the lot to deliver the goods.
Employee Actions at the Time of the Accident
In order to file workers' compensation, the employee's actions in the parking lot immediately prior to incurring the injury should have been reasonable in nature, and reasonably connected to the employee's work duties. If the employee engaged in horseplay -- such as chasing a co-worker around the lot -- or some other negligent action that the employer did not direct, he is less likely to have the claim upheld than if he was simply walking to collect a file of work documents from the trunk of his car.
\Time the Accident Occurred
If the accident occurred before or after the employee's regular working hours but the employee was performing activities reasonably related to the course and scope of her duties, the employer is likely to be responsible for providing workers' compensation payments. For example, if the employee arrived an hour before the official start of her shift to get caught up on some paperwork, she could likely claim for a slip and fall in the parking lot. On the other hand, an employee who parks in the company lot when attending a baseball game on the weekend is much less likely to have a valid claim -- unless the baseball game was a company-sponsored perk.