When your child turns 18, most of your parental rights expire. You are no longer legally allowed to view their private medical information and you cannot make financial decisions for them. You can't make life-changing choices for them anymore, such as selecting the school they will attend or stop them (or make them) join the military services.
There may still be times when they need your help though. For example, if they are incapacitated and cannot make medical choices for themselves. After your children turn of age, you may want to schedule a time to sit down with them and help them make the legal documents they need to help them in the event of an emergency.
Three legal document to consider having your 18-year-old sign
Healthcare Power of Attorney
A Medical Power of Attorney (POA) allows your child to assign someone to make medical choices for them should they become incapacitated. This document becomes important if they become injured, suffer a major illness, or if they require a major surgery.
Living Will
A Living Will often called an Advance Health Care Directive, is a document that outlines what life-saving or life-prolonging measures they want to be performed in an attempt to keep them alive.
Power of Attorney
A Power of Attorney allows your child to appoint someone to manage their finances should they become unable to or simply don't want to.