In person: Visit one of office locations to complete the Business Property Statement. All businesses operating in the City of San Diego are required to obtain a Business Tax Certificate.Find information about rules and permits on the state's CalGold website. Businesses in County unincorporated areas may need to file a fictitious business name. If the business operates under a DBA (Doing Business As) or FICTITIOUS. A Business Tax Certificate is not transferable in the case of a change of ownership. The new business owner must apply for a new Certificate. Property owners and managers doing business under fictitious business names must file and publish fictitious business name statements. You'll have to fill out a San Diego Business Tax Application. You'll have to fill out a San Diego Business Tax Application.