Obviously it depends on the period of time involved. It also depends on whether the carer came through an agency or not as they would take their cut.
Also the cost of care fees and carers are rapidly rising.
I would ask for details of the employment without asking for documents . That way the confidentiality of the carer does not come into it as they do not have to provide personal details.
However remember that it they paid a bit more than the going rate so be it. There is always a top , middle ,bottom rate.