Vehicle signage falls into two basic categories: permanent and temporary. Before you affix signage to your car, however, check the laws that regulate what you can and can't do in the interest of publicizing your company's products or services.
1. Commercial Vs. Personal Vehicle
In some states, using a vehicle for business purposes requires that it be registered for commercial rather than personal use. Placing a magnetic sign on your car door to advertise your business can be interpreted as commercial use of the family sedan. If you register a vehicle for commercial use, its insurance coverage must match its registration. Driving an improperly registered vehicle can yield a ticket and a potentially expensive fine if a police officer pulls you over. Before you spend the money on removable signage, verify that your state or municipal laws won't force you to change the way you classify your car and the amount you spend to keep it on the road.
2. Advertising Restrictions
Homeowners' associations and neighborhood covenants can regulate the kinds of vehicles you park in front of your house or in your driveway, even if you own the property. If your HOA prohibits you from placing advertising messages on your car, you may be forced to attach a magnetic sign after you leave your home and take it off before you return at the end of the day. Verify that you know how to apply and remove magnetic signage without damaging the vehicle's finish or the sign itself.
3. Visibility Requirements
Most magnetized signs fit an area smaller than the panels on a car door. Their dimensions alone mean that these advertising materials can't obscure visibility or cover up a license plate. If you graduate from door-mounted signage to vehicle wraps, which can cover your entire car, check local laws to be sure your graphics don't violate regulations that cover visibility into and out of car windows. A window-covering advertising wrap on a full-sized city bus doesn't interfere with the driver's ability to see, but an equivalent application on a passenger car could fall afoul of laws that regulate window tint and other applications.
4. Other Considerations
Tax laws allow you to deduct portions of the cost of owning and operating a business vehicle if you meet specific eligibility tests. Affixing a magnetic sign to the family SUV and trying to deduct your car payments can be grounds for an audit, as the IRS and other taxing authorities monitor easily abused portions of tax law for signs of impropriety. The cost of having a magnetic sign designed and manufactured may constitute a valid advertising expense even if you can't write off the larger cost of the car itself.