The only transaction that you may process for another person is a renewal of registration. All other transactions i.e. transfers, new registrations, plate changes, duplicate registrations, and decal changes need to be completed by primary owner only. There are additional forms that need to be signed while processing these transactions, and a signature of the primary owner needs to authorize the transaction. If the primary owner can't conduct the transaction, they will need to fill out a notarized Power of Attorney Form (PDF) for motor vehicle purposes only.