Multiple PRs to be fulfilled based on request date but Invoice to be done monthly

Summary:

We have a customer requirement, wherein the customer has different BUs in a particular region/Entity. Every BU raises Grocery/Stationary requests to a predefined supplier on a regular basis.

The customer currently sends the PR details to the supplier - the supplier fulfills the request, then end of each month all the PRs for that month are clubbed together and converted into a single PO for that supplier.

The main reason being conveyed by the customer for this is to save the time and effort to process more number of Invoices instead of 1 ( The ratio is around 100 to 1).