For the most part procurement is seen as a value shop (problem solving) business. Activities centre around acquiring the problem, finding options choosing and implementing the solution and controls over the process. Our CSO has further extended that by adding in a second business type - value network (multi-sided platform). The procurement service negotiates pre-purchase agreements that establish prices and terms, from which the clients (departments) merely have to make a call-up indicating quantity or statement of work. We call them standing offers, in the US they are known as blanket contracts. This business centres around making the information available, providing the creation and access to the agreements and managing the infrastructure to support that business.

If we look at procurement as the business line here, not the company as a whole, the question about who is the client is interesting. Ultimately I see the client is the external body for whom the value proposition is a delivered good or service. The question becomes whether the project manager is a partner (providing knowledge direction and project management) or a client in themselves. If they are the client, what is the job-to-be-done for them you are helping with, and what need of theirs are you satisfying - that is the best way to determine the value proposition for that segment. It doesn't necessarily need to be a money relationship.

Anyways remember, BM is an art not a science, there are no approved solutions only great ideas.

My experience is with the department that serves as the central service organization (CSO) for whole government. They have a stronger role than a procurement service might have in your frame of reference. The CSO has, by legislation, the authority over the purchase of goods and the purchase of services over $2M. In turn, they delegate authority to the departments to purchase goods up to their allowed level. In that the CSO has a stronger influence over how procurement works.

The battle of influence - who owns the relationship with the suppliers - is a very common one in procurement services. Because authority ultimately rests with the CSO, they have the major control over dealing with the suppliers. That does not stop many departments from having "special" relationships with certain suppliers in their sphere of control.