Name changed.
Assuming you are in Australia, Child Support is your contribution towards your children’s everyday living costs for the time they are not in your care - state schooling, food, rent, gas, elec, clothing etc. It is NOT for allowances, phone plans, extra curricular activities, presents, outings etc as these are not necessities.
In a Private Collect arrangement you and the other parent can agree that payments for things are in lieu of Child Support - so your ex may agree to what you are paying - however if the receiving parent no longer agrees to this, then he can request the CSA take over collection at anytime and request up to three months arrears for payments not received. In your circumstances he would likely be awarded the three mths arrears as allowances, sport activities, money for going out, birthday presents etc is not child support.
If you ex was to call CSA they would recommend he ask you to pay the money directly to him and if you refused he could request CSA collect (and up to three months arrears) immediately. They will immediately set up salary deductions to ensure payments from you.
Based on your list, you are underpaying him $4500 a year. You’re also putting all “expenses” onto him (deducting allowances, phone plans etc from Child Support he is entitled to receive. If you both agree to these things for your children you should share the cost. You are paying it out, but reclaiming it from Child Support you should be paying in addition to this cost, which means your ex is actually paying for all these things). It’s also quit sad that you think your children’s birthday and Christmas presents should come out of money to support their everyday basic living costs.
To people asking why you pay Child Support when the children are in 50/50 care, it’s to ensure the children have a more balanced lifestyle and benefit from both parents income, regardless of which house they are living in.
I think you need to think how’d you feel if you were the receiving parent and your ex was counting allowances, phone plans and outings as child support. I’m sure you wouldn’t be happy with it, as allowances and trips to the pictures doesn’t put food on the table or pay the rent.