The first indication is the DMV will let you know when your car will require a smog check. Smog checks are not required for a cars first 6 or 7 years of ownership if bought new. When you get your registration notice and it indicates a smog check is needed READ IT CAREFULLY because your vehicle will either require a STAR certified station, a test only (no repairs done on site) station, or a general state approved smog check station. A smog check is also required upon private sale of a vehicle to a new owner in order to get the registration transferred.