How long intill i get my back child support tax return?

IRS will not send your mom any money. Their job is to follow instruction being sent by the State Agency through the Financial Management Office of Treasury to intercept your dad refund (most of it or certain amount), then after processing the deduction, they will send letter to your dad explaining to him what happened, then the Financial Management Agency, who will send the deducted money to the State Agency that govern the Child support, then will be sent to your mother.