Sales Tax Vendor ID Number:

This service is optional. If you think that your business is required to collect sales tax from your cutomers then legally you can not legally operate the business in your state without obtaining Sales Tax Vendor Identification Number.

If you are selling products or offering services that is taxable you must apply for sales tax id number in your state. The process of getting a Sales Tax ID is called obtaining a "Certificate of Authority", "Sales tax ID Number".