How to make a mass update to sales tax, vendor, or classification/attribute
On the web portal - (retailcloud.com - 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