If it is the owner who is asking, that would be an emphatic yes.  An owner has a very vested interest in who the subcontractors and suppliers are to the general contractor.  Under the Florida Lien Law, if the general contractor fails to pay a supplier or subcontractor, then the owner may have to pay if the subcontractor or supplier files proper notices.  In fact, the State has developed a law that the owner has the right, at any time, to request in writing a list of all subcontractors and suppliers who have a contract with the general contractor.  By law, the general contractor is required to furnish the requested list within ten days of receipt of the request.