Certificates have the scope of a quality management system. Therefore, unless all sites use the same QMS and are governed by a corporate senior management team, you can not apply for corporate certification.
Nevertheless, there will be most likely similarities between the QMS of each site and possible some corporate policies, which need to be adhered at every site. In these cases it is beneficial to use the same certification body for all sites. That will support your corporate goals and objectives and the certification body will build up experience with it throughout audits at each sites. The latter will make certification audits more effective. As a corporate you may work with your certification body to allign the audit agenda for each site so each will be as valuable to you as possible.
