My ex wife walked out on me and my children 3 years ago.
I have 3 children, 2 boys aged 15 and 12 and a daughter aged 9.
The boys live with me full time and my daughter goes to her mothers every Wednesday and alternate weekends.
My issue is I'm not sure what her CSA payment covers. She has her own business and pays herself a dividend to reduce her tax, this in turn reduces my money as she doesn't declare everything she earns. i.e - mileage for her car, money towards a home office and the worst one cash or payments direct into her personnel bank so not through the business.
All 3 of my children have many activities, she pays for just one. I have to pay for the everything else.
I constantly argue with her over this plus my boys school bus passes, school uniforms etc. To her its always a battle and trying to get one over on me, she cant see the damage she is doing to the children by making a battle over everything.
I am after some kind of definition on what the CSA pays for.
There really isn't a definitive definition out there. In the main it covers food, clothing and shelter.
Activities are a parental choice for the development of children and as 2 of the children live with you the activities you mention really are a choice for you based on your own affordability. After all there are many parents out there who cannot afford any activities at all hence CMS does not really cover them.
Beyond this it is what the parents can mutually agree to. Sometimes it can feel like the amount of CMS you are getting doesn't cover the cost of bringing up the children but there are numerous cases where CMS significantly more than covers the cost
If you believe you ex is concealing income etc then it may be worthwhile reporting her both to HMRC and the CMS who can investigate although it isn't a quick process.
All the best.