It would be a good idea to have a Tax Number field for the ship-to addresses. There are fields for Tax Area Code and Tax Liable but not a Tax Number for the ship-to's. If a ship-to is tax exempt, the company must have the Tax Number for the state that ship-to is in. This is very easy to add as a custom text field, but should be included with the "out of the box" functionality as it is a requirement for all companies to have this on file.