"Vehicles registered in areas subject to the biennial smog certification program are required to submit evidence of a smog certification every other renewal period. Owners of vehicles six or less model years old will pay an annual smog abatement fee for the first six registration years instead of being required to provide a biennial smog certification. The registration renewal notice mailed to you by the department will indicate if a smog certification is required. If a smog certification is required and you have not had a smog inspection, you may still pay your registration fees to avoid any late fees. However, you will not receive your new registration or year sticker until the smog information has been received by DMV. " - From DMV website...
Thanks for the clarification Matt... I knew it was a while but forgot it was 6 years! Time to modify those cats...lol