Level 1

Add Inventory Cost to Existing Items

We are a manufacturer & distributor that has used QB's Enterprise for 6 years.  We don't use the inventory for costing, but we do use it for sales.  Currently, all costs are zero and therefore selling them does not affect Inventory or COGS.  We would like to start using QB's for costs as well.  When I do add cost to an existing item that has sales history and then sell it via invoicing, QB's is not recording the cost in Inventory or COGS?  But, if I add cost to an existing item that has no sales in the past, then QB;s records the cost in Inventory and COGS.  How do I add cost to existing inventory items with prior sales?  I don't want to start over, as we would lose our history.  Thanks!