I'm going to assume you mean property tax, since you are a buyer and we're all here at Trulia. Property tax in San Francisco is set at 1.163% of your purchase price. In California property taxes are due in two installments across the fiscal year. The first half of the fiscal year spans from July 1st through December 31st and is due on November 10th every year. However, they don't become late until December 10th. The second half of the fiscal year spans from January 1st through June 30th and is due on February 10th. However, they don't become late until April 10th.
You remit property taxes to the Office of the Treasurer & Tax Collector. For more information and to view your property tax bill online, follow this link: http://www.sfgov.org/site/treasurer_index.asp?id=98446