Your kid is now 21 but you are in arrears with payments which accumulate monthly interest fees is there anything I can do It keeps going up instead of down?

If you are referring to child support payments - regardless of whether your minor is 21 or not. If you owe back-support, you will ocontinue to owe it until you are caught up to whatever would have been the final amount of the final payment at his 21st birthday. The interest will continue to accrue until your obligation is paid off.