I would like to know whether a parent can file for child support after the child has become 18 years of age?

Have no not filed years ago?? If the child is in college, it may be possible to help pay the college expenses.

If you have a support order already in nplace you can collect up to a certain amount of years in arrears.
You need to talk to an attorney in your state. The laws vary greatly by state.

I would like to know whether or not a parent can file for child support after the child has become 18 years of age?
You can request back child support