Yes, report him! The earlier the better it can take CSA years to catch them or reconcile payments. My ex hasn't paid CS for 3 years and when his tax return adjusts the payments back up he rings and says he has lost his job and earns under 18,000 which means he gets away with paying noting! It has been 3 years and ca hasn't reconciled his tax with payments, apparently there are over 220,000 cases unreconciled in Australia.