Any advice on dealing with the CSA would be appreciated

My boyfriend has been split up from his baby’s mother for over 8 years. We have her every weekend – Fri, Sat, and late on a sunday. We have at least 2 weeks away a year and have her every other christmas day and new year. If she does not stay on christmas day we have her boxing day until new years eve. She is 11 and recently started senior school. We paid for her uniform and a school trip. Any clothes she needs we get them.

For the last 8 years my partner paid £20 a week. My boyfriend is self employed and from february had hardly any work so stopped paying the £20 but still had has her every week, still had holidays, trips out, clothes etc. and instead of paying the £20 has been giving his daughter £10 for her cashless card at school. The mum and her boyfriend both work. She has recently contacted the CSA cos she was not getting £20 (infact she was getting alot more).

Anyone know how the system works?

As I think he has been very fair.

Any advice would be appreciated.