The California Highway Patrol is starting a major crackdown on state residents illegally driving vehicles with out-of-state plates.

The CHP officially kicks off the license plate sting today — asking motorists to jot down suspicious tags and enter them into an anonymous agency Web site.

Officials estimate the state could bring in up to $10 million in additional revenue if the project succeeds.

California law requires motorists to register their cars with the Department of Motor Vehicles within 20 days of establishing residency and getting a job. But many register their vehicles in states with cheaper fees while living in California.

The average cost of registering a vehicle in California is $130 and vehicle registration is a major source of revenue for local governments, the CHP, the DMV and other agencies.

DMV officials say registration-related fees totaled $4.3 billion in revenue in 2003.