My daughter's fourteen year relationship ended in January when her partner left her and the two children. They agreed that, rather than pay maintenence, he would pay the mortgage and the fuel bills for the time being. Since then he has been living with his parents. She applied for and received Single Parent Working Tax Credit. She says that there is nowhere on the application form to declare the financial arrangement, but she did bring it up in one of the conversations, and was told that it made no difference. She also applied for and received council tax single occupancy discount. The bills remained in his name and they came to her home where he collected them when he visited the children, which he does frequently. HMRC are now alleging that they have been living together and are demanding proof to the contrary. We have offered various things such as letters to him from HMRC at his parents' home, the fact that he has registered a business there, and other correspondence, all of which is met with, "that doesn't prove anything." We have offered statements from all sorts of respectable people who know of and can attest to the separation but are simply told that that isn't evidence. They say he has not changed his driving licence address, which he admits, and seem to think that is clinching evidence. They say he has applied for finance using my daughter's address, which he denies. He does, however, admit that he has opened a new bank account using his driving licence with its old address, as proof of identity and residence. HMRC have told her by phone that they are stopping her benefits immediately and that she will receive a letter telling her how much she must repay, and that there may also be an additional penalty. I also fear there may be a criminal investigation. I accept that there is good reason for HMRC to be suspicious and to carry out checks, but the fact remains that she has been honest throughout and has been living alone since January. It seems that whatever evidence she offers to the contary is arbitrarily rejected. All this is down to the indolence and stupidity of her ex-partner, but it is she and the children who are suffering. What can we do?