Retailers engaged in business in California must register with the California Department of Tax and Fee Administration (CDTFA) and pay the state's sales tax. Who must obtain a seller's permit?What does engaged in business mean? Apply for a New Business Tax Certificate online or at the Business Tax Office. Refundable business registration fee plus special fees. List the products you produce: 3. If you are not registered for GST, make purchase order which will show all prices as GSTinclusive and make no mention of GST. This is the total of state, county and city sales tax rates. Importing Into the United States provides wide-ranging information about the importing process and import requirements. We have made every effort to include.