If you are planning to conduct business in the City of Riverside you must obtain a City of Riverside business license, also referred to as a business tax. Invoices can either be mailed to PO Box 868, Riverside, CA 92502 or email us.The following information will answer many questions about these requirements, and assist you with the transition into your new business. A Fictitious Business Name shall be filed within 40 days of first transacting business. Once registered, it is effective for 5 years. Business Licenses and Permits. The following links will help ensure businesses are properly licensed, and, if needed, registered with the state. Letter of Intent: The letter of intent should spell out the proposed price, the terms of the purchase and the conditions for the sale of the business. Food protection course for restaurant managers, operators and other staff. This class is available to everyone.