Perform work or render services within San Francisco for all or part of any seven days during one tax year. Maintain a fixed place of business within San Francisco. In general, businesses must register if any of the below statements are true: Lessors of Residential Real Estate can learn more about information on business registration requirements here. San Francisco’s Business and Tax Regulations Code generally requires that every person engaging in business within the City, regardless of whether the business or person is subject to taxation, must register within 15 days after commencing business within the City.