Ex hasn't paid child maintenance based on the CMA online calculator that he has 'agreed' to for over 2 months. I know I need to ask the CMA to get involved now but how does this work? If he changes jobs do they rely on me knowing so I can tell them? He has fiddled his tax returns for years, doesn't declare half of his additional freelance work (worth thousands) so do I tell CMA or do I notify HMRC? I really wanted an amicable arrangement but his maintenance payments based on his current salary don't even cover half the childcare (which allows him to work just as it allows me to work). Advice appreciated. Thank you :-)