Hope this is the right section.
My dad moved out in August and dm has been claiming working tax and child tax credit (for dsis) since. Yesterday she got a letter saying her tax credit was being cancelled because they think df is still living with us, despite dm sending bank statements to show she is paying all bills. There are a few bills and a joint account which still have both their names on which is being corrected, but the big problem is df has no formal rent agreement with the couple he is lodging with and pays in cash.
There seems to be very little information on how to prove you've separated, dm and df aren't married so divorce isn't an option, and obviously they won't just take their word for it. As df isn't overly generous with maintenance and dm can only find part-time work tax credits are essential. Can anyone advise?