They do reassess at sale...however, say we bought this month, our taxes would be what they were for the previous owner for the remainder of this year. So we’d be paying the same taxes, the owner would have had, at least till the end of the calendar year.
This can work in your favor if you’re buying a house for investment (which will not have a homestead exemption) but if the previous owners claimed homestead exemption for this year, you get to get in on their rate till the end of the year.
We’ve owned our present home for 20 years and pay relatively low taxes because of a cap that limits the upward assessment to a certain percentage each year. But they only reassess every three years in our county.
Your county probably taxes for the previous year. This is common. The value you are being taxed on is a year or more old. I just paid half of my 2008 taxes the first of the year and will pay the second half in mid-year. The valuation was set in 2006 or 2007. So, if they were to lower the value now, it wouldn't show up in taxes until the 2010 tax bill, which you would start paying in 2011. At least that's how it works some places.