"A business-use endorsement is just so you and the carrier understand each other that this vehicle is used for business purposes," Kuryak says.

In some instances you may not need additional coverage. Say, for instance, you're a self-employed writer and drive occasionally to your literary agent's office. In that case a personal policy likely would suffice, and a business-use endorsement would not be necessary, Kuryak says.

But if you drive frequently for business, the insurer may require the endorsement or have you upgrade to a commercial policy.

The choice will vary according to your circumstances and the insurer. A business-use endorsement on a personal policy may be sufficient if you're a sole proprietor, use only one vehicle for the business and you can purchase high enough coverage limits to protect you and the business, Gusner says.

3. Understand when a commercial policy is a must.

Some vehicles and uses are disqualified for personal auto insurance, and you have to buy a commercial car insurance policy to have coverage.

"You're not going to get a dump truck on a personal policy," Kuryak says.

You might even have a hard time getting a pickup or van used for business on a personal policy.

Say, for instance, a self-employed handyman uses one vehicle, with no equipment attached, to drive to homes to bid on projects.

"If he is using a car, a personal policy may be all he needs," Kuryak says.

But if he's using a pickup or van, the insurance carrier might require a business-use endorsement or might not issue a personal policy on the vehicle based on the customer's occupation as a self-employed contractor. The insurer will assume the vehicle is used heavily for business purposes.

"Also, will the contractor have signage or a wrap on the vehicle advertising his service? That just screams business use," Kuryak says. "To be safe, the contractor should indicate business use to their personal lines carrier and see if they will accept the risk. If so, all is good. If not, then purchasing a business policy would be needed."