What is the best practice to change the cost of a stock item?

Summary:

Item received through PO is in use. How can we change the cost of the items without negatively impacting the stock accounts and Inventory reports reconciliation? What would the impact of the cost change be?

Content (please ensure you mask any confidential information):

An inventory item has been received in stock via a PO with cost A. The item is currently being used via Transfer orders. The cost of the item in stock should change to cost B. What is the best practice to change the cost of the items without negatively impacting the stock accounts and Inventory reports reconciliation? Kindly provide your guidance.