refer someone back to someone or something
to suggest that someone go back to someone or something, such as the source. I referred the client back to the lawyer she had originally consulted. Tom referred the customer back to the manufacturer who had made the shoddy product.
refer something back to someone or something
and refer something backto send something back to someone or a group for action. Dr. Smith knows more about this kind of case, so I referred it back to him. They referred back all the bills.