In-person help at the San Francisco IRS Taxpayer Assistance Center (TAC) is available by appointment only, between 8:30 am and 4:30 pm Monday to Friday. To make an appointment call 844-545-5640. The TAC is located in the south lobby of the Phillip Burton Federal Building at 450 Golden Gate Avenue (between Polk Street and Larkin Street) and government-issued photo ID is required when passing through security upon entering.