They should stop automatically. If they don't then call the bank and put a block on the money being withdrawn (provided you agreement does end when they turn 18)
You have to petition the court for child support to stop even if it's decided at 18yo. The system differ in different states. If the age is not mentioned in your child support agreement it will not stop automatically at all.
In most cases, child support stops the month the child turns 18 or graduates from high school, whichever comes last. In some cases, however, the court can be petitioned to provide support while a child attends college. In that case, child support can only be stopped after the 18th birthday if both the petitioner and respondent agree to this change in the original court records. Be sure to get it in writing for your own protection.
Motion to modify current and future child support. Make request to child support enforcement.
Generally, there are no steps. You can just stop paying beginning the month after the child's 18th birthday.
Only in American Samoa see link below
on her birthday
Make an official request with the court that issued the child support order.
You stop paying for child support when your child turns 18.
You can stop child support payments on the grounds that the child is not your biological child only if you did not know that when you agreed to the support, and if a Court approves your request to stop.
In Colorado, child support will stop at the age of 18 or when the child finishes school. There is a possibility that the child can receive child support if the child goes on to college.
The duty to pay child support stops at age 18 except when the child has not yet finished high school, and in that case it will continue until the child completes high school, but not past age the child's 20 th birthday.
your child attends community college when will support stop
Assuming the child has aged out, you make an official request with child support enforcement to have the order modified. see link below
Make an official request to Child Support Enforcement, or file a motion to modify. see links