RE: Edit - Average Cost Calc. Overview
Is your value entry blank? If yes, you have an issue.
If you have inventory in BC, then you have value entries.
The issue here seems to be around how standard cost is used. Let me clarify:
With standard cost method, the inventory cost, therefore, inventory value is not equal to the purchase price.
For example. Item A standard cost £10.00. You receive a purchase invoice at £12.00 each, your inventory cost will still be £10.00 with a £2.00 variance.
The purchase price in the invoice does not change the item standard cost. Nor should users change this value after receiving an invoice.
The standard cost of an item is usually changed after year-end or when you close an inventory period. If you want your inventory cost to be updated depending on the purchase price, you should use FIFO or Average costing method, not Standard.
If you need to see how much your company paid for an item overtime whilst monitoring the difference between the price paid and the standard cost you can run a report on purchase invoice lines (Posted purchase invoice lines).
Alternatively, you can use the value entry table to see all inventory costs allocated to an item like purchase variance and landed costs (Item charges)