let's say you owe $xxx each month for current child support. Is your paycheck from work being garnished at that amount ? If not, is it more such that you are also paying an arrears payment? If it is less,then you are adding to arrears. If you are continuing it get further and further behind, it is possible your arrears grew to an amount where they took notice. Because at some point you didn't pay what you owed (which is why you have arrears in the first place).