Child maintenance

[Faloola88]

Hi all, where do I even start.
Me and kids dad broke up 6 years ago. He is only available in a Sunday afternoon to spend time with them as he is always working. Me and their dad have a history of domestic violence, him towards me. I cant even begin to explain his evilness toward me....
Anyway I set me feelings on him aside and still allowed my kids to see him because they love him.
He has always paid me 100 per week for both children, a agreement between us, never had issues with him paying me.
His now self employed, had been for 2 years, has his own company etc...
We argued recently as he missed a couple child maintenance payments and he then sent me a screen shot of a online calculation he done from the child maintenance website.
He put down he earns 12 grand a year so they calculated that he should pay me 36.82 for both kids for a week!!!!
Every penny has always gone on my children, my 12 year old son is 6 foot an wears size 10 shoes, my daughter is 11.
The point is he lied about how much he earns a year! 12 grand! He dont get out of bed for less than 250 a day doing private construction work. I know alot he does cash in hand so I have reported him to hmrc as I dont believe his paying his taxes. I've also made a application to csa for them to look into it.
I know this sounds spiteful and I really am not money grabbing but my kids deserve and need that money! Im being treated for PTSD because of my past, this man bullied me, put me in hospital while pregnant with our son cut my neck with a blade, he was awful to me!
I feel very resentful because he seems to have absolutely everything and he is a evil man, yet I do absolutely everything for my kids and struggle on a daily basis.
I do believe he deserves to be caught out, do you know what hmrc will do and if they can catch him out working cash in hand as I believe he doesn't pass much money through his company and it seems he changed his company this may, to avoid tax? I dont know my id really appreciate some advice.
No negativity please

CMA also asked me how many nights he had the children, as he’d exaggerated. I told the truth and they took my word for it.

I have had the same problem for 6 years. My ex lives off expenses, doesn't draw a salary and then liquidates the company one day short of 2 years so the books aren't looked at. He then invests all the dividends that he has withdrawn into another company and starts all over again. CMS seem to be able to do nothing. They have investigated him and asked how he paid his mortgage and very expensive house. He then sold his house, his car conveniently got stolen and he moved in with his girlfriend and claimed unemployment benefit. I was told to report him but fraud department do nothing. He drives around in his mother's disability car. He has just bought a very expensive house and got a paid job now that my youngest has turned 18. He is a vile man who has never supported his children. His 3 children who are now all adults still see him occasionally but they don't respect him. I have been in contact with the head of CMS but they are unwilling to accept that there is anything wrong with the system. There really needs to be a petition about the self employed parents not paying. The law needs to change and they need to be made accountable.