This is the final week Iowans can donate vehicles, boats or airplanes to charity and get the best tax break. I-R-S spokeswoman Donna Migazzi says a new federal law goes into effect on January first that will mean less of a tax write-off for donors. Taxpayers now can take the “fair market value” price for any vehicle they donate, but when 2005 arrives, they’ll be limited to the amount of money the non-profit group actually gets for the vehicle at auction or when it’s sold. When you donate a vehicle, Migazzi says you’re supposed to take into consideration things like: make, model, year, mileage, condition and other factors — but people often don’t do that and “mark up” their price. She says the new law will give the donor exactly the tax deduction they deserve, no more or less.It means if you donate a car next year worth four-thousand dollars and the charity only gets 800-dollars for it, your tax deduction is 32-hundred dollars less than it would be this year. Charities are braced for a drop-off in donations, especially in high-dollar vehicles, but Migazzi doesn’t think the new law will have a significant impact.