Now that your child is an adult, he must realize that everything you choose to provide for him is a privilege, not a responsibility. You’re not there to coddle a young child anymore, but rather to guide a young adult. It’s his job to follow the rules of the house, contribute in ways that you feel are appropriate and accept the consequences of his actions -- even if that means handing over the car keys for coming home late or paying out of his own pocket for the fresh dent you found in the morning.
Make the rules, responsibilities and consequences well-known to your child. Sit down and have an open discussion about your expectations and the consequences that will ensue if he fails to abide by those rules. If you’d like him to be home by 11 p.m. during the week because you have to get up for work the next morning, explain the rule and your reasoning and let him know what will happen if he is not home by the designated time. If it’s his job to get his laundry to the laundry room by Saturday morning, let him know that it won’t be washed if it isn’t there.
Provide your young adult with an opportunity to voice concerns and objections to your rules and responsibilities in a reasonable and rational manner. Your child is old enough to pose an argument without launching into a temper tantrum, and he might have valid alternatives to rules that you would be willing to consider. For example, if he works late on Wednesday night and would like to stay out later, you can agree to make an exception for one night or allow the exception but have him stay at a friend’s house for that night instead.
Try involving your young adult in choosing appropriate consequences. For example, if your 18-year-old has been late on multiple occasions picking up her younger sibling from soccer practice, she might accept responsibility for her tardiness and how it has left her brother standing around after practice numerous times. Now, she can recommend that she make amends by spending an afternoon with her brother, taking part in the activities he chooses for the day. Your child's willingness to discuss consequences rationally demonstrates that she already understands her wrongdoing and is acting maturely to make amends.
Write a contract detailing the rules and consequences you have discussed with your teen to provide a constant reminder of your expectations.
Be consistent with enforcing the rules. If your child realizes that you are lax in handing down consequences, he might be more likely to bend or break the rules, treating them more as guidelines than expectations.
Allow your child to experience the natural consequences for her actions. If your 18-year-old spends her car insurance money on Friday-night outings, don't cover the insurance bill for her when it comes due. Instead, you can insist that she refrain from driving the vehicle until it is properly insured.