That's fair enough. I can understand how frustrating it must be! That is partly why I would suggest a formal, regular agreement. Then he has done his part and she will have to manage her own finances. Also, he then has proof of what he has given. That way, all the finances don't get "muddled together." He should have one agreement with her for any children that live there- and that's it. Should be no need to provide food or clothes then on top of that, unless he particularly wants to. If you genuinely (objectively) think she is an unfit mother who will not feed and clothe the children, that's a different issue really and probably best to speak to Social Services. However, if she involved the CSA, they would force him to give her money directly. Would you not expect the same if he moved from yours?