Leveraging procurement across companies and company groups

A method and system for providing procurement services to customer companies. A user profile for each user, in a computer database, specifies: (i) each user is authorized by a first customer company of the customer companies to access procurement resources and the procurement services for purchasing items and (ii) the first customer company and a first company group of related customer companies. Access to volume discounts with respect to vendors is provided to all customer companies in the first company group. Companies are authorized to have access to and share each procurement resource, by providing a resource profile specifying for each procurement resource a set of customer companies authorized for accessing and sharing each procurement resource to be shared among the users. Access to the procurement resources is controlled resources based on: the first company group, the first customer company, and the resource profile for each procurement resource.