if your husband is on the old system the claim by the child's mother was done before 1993! i'd definately ring the csa and ask them why theyre now taking into account your wages when they havent before, also if you have children that are living with you they should take that into account and deduct some anyway, the csa have a online calculator also. if they are now taking into account your money etc then u also need to make sure they dont backdate it if theyve never done it before, my friend works for the csa and it's in such a mess