QuickBooks allows only Average costing for inventory, while Sage 50 allows you to cost items based on Average costing, LIFO (Last In First Out), and FIFO (First In First Out). If you choose to convert transactions, Sage 50 must ensure that inventory costing remains the same and all inventory items will be converted with Average costing. You will NOT be able to change the costing method of those items to LIFO or FIFO in Sage 50 after the conversion.
If you do want to CHANGE the costing method of your items, you must choose NOT to convert transactions. Then, you will be given the opportunity to select a default costing method for inventory after the conversion and you will be able to change the costing method of the items that are converted.
Note: You must change the costing method in Sage 50 BEFORE you use the items in any transactions.