How to make a mass update to sales tax, vendor, or classification/attribute

On the web portal - ( - select login)

Go to Management>Inventory>Item

Search for the items you want to modify (this can be by selecting the category from the dropdown) and press search

You will get a display of all items that meet your filter criteria - select all or a few

Press Mass Modification and select what you want changed on those items>Save

This will update those items with the new information