If you’re considering purchasing a home in San Francisco, you should be aware of the fundamentals of property taxes before you sit down to sign your loan documents and complete your purchase. Property taxes are something you don’t really think about until you’re scrambling around trying to pay them on time.

So here’s what you need to know, in a nutshell:
Property taxes are based on a percentage of your home’s value. The property tax rate changes slightly each year. For example, for the tax year 2011-12, the rate was 1.1718%. But for 2012-13, it’s 1.1691%.

Property taxes are charged on a fiscal year, starting on July 1 and ending on June 30. Taxes are billed in two equal installments, and the bills are sent to homeowners in the last week of October. The first installment covers the period from July 1-December 31st, and it’s delinquent if not paid by December 10. The second installment covers the period from January 1-June 30, and is delinquent if not paid by April 10.

Don’t miss out on the homeowners’ exemption. If you own and occupy a home on January 1 as your principal place of residence, you’re eligible to receive a reduction of up to $7,000 of the dwelling’s taxable value in the form of a Homeowners’ Exemption. You have to contact the Assessor’s office and file a claim. Once you receive the exemption, you don’t have to file the claim each year as long as you own and occupy your residence.

There are various parcel taxes included in your bill. San Francisco loves to put measures on the ballot that involves some sort of annual parcel tax. So you may see a laundry list of small-scale charges on your bill. For example, there’s the Mello-Roos Community Facility District tax, which is about $32 per year. (Mello-Roos districts are designated areas which have issued bonds for various community facilities. There are two districts in the city, one encompassing the entire city and the other in a small area South of Market.)

Don’t forget about supplemental taxes. When a property changes hands, the Assessor’s office reappraises the property and bills the new owners for the difference in taxes resulting from a higher assessed value. The Assessor issues you a supplemental assessment bill which is prorated based on the number of months remaining in the fiscal year ending June 30. And it works both ways; if you paid less than the previous owners for your home, the Assessor will send you a refund for the difference on the tax between the old and new property tax base.

Do factor in property taxes when you calculate your overall monthly payments. Along with the estimated mortgage payment and insurance, you should break down your total property tax amount on a monthly basis so you can get an accurate idea of your true carrying costs.

For more detailed info on property taxes, hit up the Treasurer and Tax Collector section on the SF Gov Web site.