If you can’t agree how much child maintenance one parent should pay the other, you can ask the Child Maintenance Service to calculate it for you. The answer you have. You can use this system to calculate how much child maintenance you should pay. Csa will treat your first child as your only one and deduct 15% of your wages and not include your second child which you pay for.
Csa will take into account that you are paying for children ensuring only 10% is going to first sons mother. But the CSA has to use the same rules for everyone.

However, 70% of the closed cases still have unpaid arrears attached to them. HOW IS CHILD MAINTENANCE CALCULATED ? Understand how arrears are calculated. Sometimes, arrears will have built up because your child’s other parent failed to provide information. In this case the CSA may have made an interim maintenance assessment or default maintenance decision.



