If you are running a home-based business, for example, you may assume your personal auto insurance is enough, but this isn't always the case. Unfortunately there is no black and white answer that dictates when you need to buy a rider to your personal insurance policy to cover the business use of your car.

Talk with your insurance agent about how often you use the vehicle for work, and he or she should be able to help you decide what's best. If it turns out you need to add business coverage, you can expect to pay about 10 percent more than you are currently paying for your personal policy.

If your business owns a company car, however, there's no way around buying a commercial auto policy, which is meant to protect your business's assets in the event of an accident. This is an absolute must.

The gray area comes in when your employees use their personal vehicles for business purposes - even for something as simple as trips to the post office. If they get into an accident, their personal insurance will kick in, but anyone involved in the accident can also come after your business.

You need a hired and non-owned policy in this situation. It not only protects your business if your employee is involved in an accident on the way to a sales call, for example, but it will make your employees less apprehensive about using their personal cars for business, since they won't be held personally liable in case of an accident (and their personal auto policies won't be at risk). This type of policy will also cover cars rented for business use.

Depending on a number of factors - from what state you live in to the type of car your business owns - a commercial auto policy can cost more, or less, than your personal auto coverage. Keep in mind, however, that prices in the auto insurance industry overall are on the rise.