How do I add someone to my car title after buying?

Adding a co-owner usually means applying for a new title through your state DMV with both people's information and signatures, and paying a title fee; some states may charge tax on transfers depending on the relationship. If the car is financed, the lender typically must approve because it holds the lien or title. Check your state DMV's website for the exact forms and fees, and update your insurance so both owners are covered.