This blog describes the change in behavior when changing vendor on a purchase requisition, and releasing the requisition to a purchase order related to KB 2973728.
Microsoft Dynamics AX2012R2 before KB 2973728
When you create PO’s from approved requisitions, the system will transfer financial dimensions from the requisition line to the PO line. If you change the vendor or add a vendor after the requisition line was approved then the vendor’s default financial dimensions will not be transferred to the PO line. See screenshot below.
For some companies this has been a problem.
Microsoft Dynamics AX2012R2 with KB 2973728
In the situation above, the business process has required that the financial dimensions from the added vendor are used on the Purchase order line. So if there is a default financial dimension on the vendor card, then that value should override the value of the financial dimension coming from the purchase requisition line.
KB 2973728 gives you the option to enable the above described behavior. You need to set up the purchasing policy to:
"Merge financial dimensions into a purchase order when a vendor is (modified or) added to an approved purchase requisition". This is done from Procurement & Sourcing > Setup> Purchasing policies. Create a new "Purchase order creation and demand consolidation" rule. Then, for the "Manual purchase order creation", check the "Merge financial dimensions ...." policy.
Furthermore, as part of KB 2973728, the Sales tax group will now always be copied from the vendor record to the created purchase order.