He has every right to ask, just like you have every right to not answer. It doesnt sound like you are abusing the CS system so what is the problem? I personally would feel obligated to ask my x where she spends the money if I am still having to buy all their clothes, pay for the extra activities, etc etc etc while driving a 10 year old car and she is sporting around in the latest fashions driving a new bmw. That is an exterme example but you really didnt give us any specifics to judge from. So again to answer your question "does he have a right?" sure he does but only a court can determine if you have to supply an answer.