Understand the critical difference between partial and full inventory sessions so that your inventory counts are correct.
When you are ending your inventory session you have the option to specify if it was a partial inventory. A partial inventory session is when you count some, but not all, of your products. For example, some establishments do a full inventory once per month, but do partial inventory of their high volume products once per week to help them know what to order.
When you end a partial inventory session, the counts you entered will be updated on those items, but any items you did not put in a count for will not have their quantity affected. If an item is out of stock, you should put in 0 for the item in at least one location so it sets the quantity to 0. Any items left blank will not have their quantity adjusted.
Conversely, for a regular full inventory session, Backbar assumes that you counted all items. If an item is left blank, it is assumed that the count is 0. Be sure when you end a full session that you have counted all your items so the quantity does not get set to 0. Before ending you will see a list of items that have not yet been counted so that you can double check.