i have no experience of this. can only dream of 50/50. but if you dont have a court order stating 50/50 then CMS will not be bothered. do you have any documents, copies of messages where you have agreed this with the ex? CMS may take that into account. are you registered with CMS?
Yes, Have agreement between us that states 50/50 unsigned but agreed at the outset and we have been running by those rules for over a year. Have a full calendar of dates that account for 50/50 but have done more. Question is do I dive in and cause a massive stink? It doesn't seem fair as technically I am the main parent here.
How many children have you got? Maybe you can look at changing some of the child benefit into your name for half of your kids before you go in head first? This will help you with the CMS. That way maintanence will in effect cancel itself out in theory, but there are a lot of factors to take into account.