Hi Losingbattle
I’m not sure about your situation, but surely the Child Maintenance service could be notified, if they haven’t already, and then they would pursue his liability, because the arrangement you have privately isn’t working? But if you’re already using CMS they also need to know he’s not complying as they have powers to enforce payments to you. As I say though, I don’t know about this specific situation. I think family income is considered, as in whether he pays for another family (as he’s living there), but I don’t know if it works the other way that a partner has to contribute. It really does rather work against single mums sadly, but call them as they will be able to clear this up for you.
warmest wishes
ts