As the real estate market warms up for the Spring buying season, sellers who are taking a hit on their sales price could be trying to recover their losses any way they can. One method is for them to reduce the real estate tax credit for 2009 property taxes at closing from the traditional 110% of the previous year’s tax bill to a more austere 100%.

While most buyers wouldn’t usually allow such corner-cutting by property sellers, a new wrinkle in the calculation of Cook County property taxes could help sellers dupe some buyers.

Late last year, Cook County Assessor James Houlihan’s office sent out a Notice of Change in assessment to all property owners. The letters indicated that the assessed valuation of most properties had been reduced in 2009, compared to the assessed value in 2008. A property’s assessed value is used to calculate the amount of property taxes each year. But this year, even though the assessed value of most properties was decreased, that doesn’t mean that taxes on each property will decrease. In fact, real estate taxes on most properties will increase in 2009.

That’s because the method the assessor’s office will use to calculate taxes will also change to charge a higher rate of tax on each property’s assessed value. To put it another way: each property may be worth less than in past years, but the taxes will still increase. No one can say for sure what the second installment of the 2009 property tax bills will say when they are sent out this fall, but one thing is certain—property tax rates in Cook County did not decrease.

Despite this fact, some property sellers are using the letters that show a decrease in assessed valuation to claim that their property taxes will go down. And they’re using them as an excuse to offer a lower property tax credit at closing. But buyers beware: a letter showing a decreased assessed value doesn’t mean taxes will be going down. In most instances, a property’s taxes will not go down unless the owners have successfully appealed the property tax rate. It’s important to consult with a real estate attorney, but unless the seller of a property can show you he successfully appealed a property tax bill, don’t take a lower tax credit at closing.