RE: Receiving of Goods and Services
As related to inventory goods; the logistics department (warehousing) is the responsible party for receiving and assuring that the quantities have been received, the quality department has a role in ascertaining its quality through sampling or any other quality assurance function. In this essence, the warehouse keeper is the one to communicate with both purchasing and accounting and deliver the required documents that items have been received. I suppose you are thinking of this level as part of the purchasing approval workflow, right ?
If so, I believe this is a completely different step which is mostly not considered part of the workflow. The workflow can be designed to include the requester, department approval, final approval, (optional) budget approval and then the purchaser. As shown in the graph below:
I don't believe that further steps should be part of the workflow such as ascertaining that products are received and the payment. Especially the payment, this is a purely accounting process which is related to the payment terms, vendor aging and several other parameters.
For the service, it is a completely different story and depend on the type of service and can differ among different organizations.
I hope that this has been comprehensive for your case. Otherwise, please never hesitate to share any further concern.