Sales tax varies from state to state, but the most common sales tax exemptions are for resellers, the federal government and the state's own government institutions, according to SalesTaxSupport.com. Many states offer exemptions for manufacturers. Check specific state laws for complete lists of sales tax exemptions.
The resale exemption is available to companies that purchase goods to be resold to a customer, rather than used by the purchasing company itself. Per the Sales Tax Institute, resellers typically must register with the state in which they qualify for a sales tax exemption and must provide vendors with a resale certificate to avoid paying sales tax. Resellers must still pay sales tax on items purchased that are not intended to be sold to a customer.