The Mental Capacity Act 2015 has a code of practice which attorneys and deputies must follow. The code of practice can be found at:
Paragraph 8.67 notes that a donor’s money must be kept separate from an attorney’s or deputy’s money and having an account in joint names would entitle a donor or attorney to deposit their money in the account and contravene the regs or to purport that the money already in the account is to some extent the donors or attorneys money.
Hope this helps. The code of practice can be a very useful tool.
Judith Naylor
Cumbria County Council