Usually there are two main tax numbers a business applies for:
Sales Tax ID - used when you are a retail business to collect sales tax, or companies that need one to purchase wholesale. Issued at state level.
Federal Tax ID - this is the ID you get when you form a company, and is used to file business taxes and also Federal Unemployment Tax if you have employees.
For Idaho, you should be able to go to:
http://tax.idaho.gov/
I think you'll need to review the information here:
https://cl.idaho.gov/applications/ibrs/ibr.aspx
If you are looking for tax info for other states, use the following link:
http://www.taxadmin.org/fta/link/
Hope this helps.