You are correct.  Sage 500 does not have any time component to the calculation of weighted average cost.  This process simply recalculates the average with each positive inventory transaction that you record for each item/warehouse combination. (If you are maintaining a negative on hand balance then this is not true and you need to remedy the negative on hand balance issues first.)

If your costs are wrong, you can utilize the Cost Ter Adjustment feature to make corrections.  These updates will have financial impacts on your system.  You will want to document the corrections and changes such that you have information in case of a future audit.  (Again, if you are maintaining a negative quantity on hand you will have to resolve that issue first.)

Ok, thank you for the reply. I'm new to Sage 500, 4 months now so I'm still learning the system. Yesterday, after posting, I found in our system that we have over 4000 of our items do not have an Average cost (timInventory.AvgUnitCost). I'm looking at the items but I do not see anything that would cause this. We have had transactions against the parts, creation dates vary from 2012-2019, every item is set to Average, etc...