There are multiple factors that may cause a discrepancy between the Supplier's catalogue and the Buyer's Purchase Order or Invoice price.
The Buyer may have ordered an Informal item with an incorrect price from a Self-managed catalogue.
The Supplier may have changed the price of the item or applied a rebate and not updated the Purchase Plus catalogue to reflect the change.
The Supplier may have incorrectly entered an ad hoc discount or price increase.
The Buyer may have submitted a Purchase Requisition while the Supplier was amending the price of the item.
(Note - the current price of the item in Purchase Plus at the time of submitting the Purchase Requisition will be the price that will be carried over to the Purchase Order and subsequent Invoice).
Price changes are subject to the Supplier's discretion. Also, beverage items that attract WET (Wine Equalisation Tax in Australia) are subject to 6 monthly price review (possible increase or decrease), also potentially at the Supplier's discretion. For more information on WET tax, please check out this article, WET tax explained.