http://search.dmv.org/dmv/california/buying-a-used-car-from-a-private-party
Once you have sealed the deal, you have 10 days to transfer the title of the vehicle from the previous owner to you. The title is the car's ownership certificate.
If you purchase from a dealership, they will take care of this. But if you bought the car from a private party, you will need to apply for a title in your name by going in person to a DMV office with the following:
* California Certificate of Title OR Application for Duplicate Title, signed by the buyer, seller, and lienholder (if any)
* Transfer fee
If there's more than one seller on the title, or more than one buyer, all signatures will be required on the title transfer paperwork.
Transfer Fees
All fees must be paid within 30 days of the sale, even if you're missing some paperwork.
* Title transfer (if registering the car as well): $15
* Certificate of Title only: $16
* License plates (regular) $16
Bill of Sale
It's also smart to get a Bill of Sale―one copy for you, one copy for the seller. You might not need this, but it's an easy backup document should there be any questions about the transaction later.
Registration
While it doesn't cost much to transfer the title, you should expect to pay quite a bit more to register the vehicle―especially if it's a newer model. You can get an estimate for the registration fees before you go to the DMV office by using the handy Vehicle Registration Fee Calculator. For an additional fee, you can also obtain personalized or specialized license plates for your new wheels.
For more information on transferring the title, read the DMV's registration and title FAQs.
Buying from Out of State
If you are purchasing a vehicle from out of state, you must file the change of ownership and register the vehicle in California within 20 days.
Make sure the car meets all the qualifications for registration in California.
To help you, the DMV has prepared a brochure about registering nonresident vehicles and has also prepared an excellent list of things to look for when purchasing a vehicle from out of state.
Nontransferable Registration
If you buy a car from another state and don't get a title for it, you'll have to undergo the nontransferable registration process. You must submit:
* Most recent title―from California or another state
* California nontransferable registration card, if it exists
If you are not the owner listed on the nontransferable registration, you must submit:
* A completed Application for Registration
* The most recent title signed by the previous owner(s), transferring ownership to you as the new owner
* A bill of sale
In some cases, the transfer of the vehicle will also require:
* A transfer fee
* Renewal fees
* Smog inspection
* An odometer disclosure
* A motor vehicle bond―if ownership of the vehicle is not proven with the proper documentation
