Self Employed ex - what is the best deal

I have a question regarding financial matters would like to apply for Consent Order (hopefully). My ex is self employed and only claims possibly 1/3 of his income.

There are no assets, pensions etc. One child from 4 year old marriage.

I am working part time (take home salary 900); receive tax credits, CB, CM 120 per month

Ex self employed 900 per month (in reality 3x more)

I am better off financially so will not ask for SM only nominal SM (as we have young child living with me)

Please can you suggest if this will ok - how often there are variations of nominal SM?
Thank you

Do you mean that he only declares a third of his income for tax purposes, and that the income he will state on any financial disclosure is actually a lie? I assume he gets paid cash for a lot of the work he does? Have you suggested to him that for anyone to make an informed decision about SM he at least needs to be honest about his income? My ex husband and I are both self-employed and it made things very difficult with agreeing a split as he became extremely creative with his accounting! I do wory that one day I will no longer be able to stop myself making the phone call to HMRC.