In order to do business with a REAL Wholesale Suppler, you will need to supply a "Sales Tax ID number".

This is called different things in different states in the US, but the reason you need it is simple. REAL Wholesaler Suppliers are not going to charge you any tax on the products they ship to your customer. At the end of the year, they have to show the IRS why they did NOT charge you that tax.

Your "Sales Tax ID number" proves that YOU are collecting sales tax on your customers' purchases. The general rule is that you only collect sales tax on the products shipped to addresses in the state where your business resides, but you should check to be sure how this is done in your own state.

The Wholesale Supplier keeps a copy of your "Sales Tax ID number" on file, so that they are not liable for the tax on the products shipped to your customers.