NEW YORK (MONEY Magazine) - These six money savers expire Dec. 31. Use 'em or lose 'em.

You can make deductible gifts to charity right up to the last minute. But do it right.

If you mail a check, it need only be postmarked by Dec. 31, even if the charity opens its mail in 2006.

If you donate by credit card, the charge must show up on your statement as having occurred in 2005, but you can pay it off in 2006.

If you're considering donating your car, keep in mind that starting with your 2005 return, your deduction will probably be limited to what the charity nets from selling it (rather than the frequently more generous fair market value).

If you set aside money in a flexible spending account in 2005, you have as many as three deadlines to remember.

You have until April 17, 2006 to file a reimbursement claim for your out-of-pocket health-care and child-care costs. You may, however, have to spend the money by Dec. 31.

A new Treasury Department rule gives companies the option to extend the deadline to March 15, but don't assume your boss has done so. Only about 50 percent of plans have, according to Hewitt Associates.

Unless Congress renews the law, 2005 will be the last time you can deduct state and local sales taxes instead of income taxes on your federal return.

If you're in the market for a car, boat, motorcycle or plane, think about buying before year-end. The IRS sets the standard sales tax deduction for each state, but any sales tax you pay on a vehicle is an extra write-off.

If you have money-losing stocks and mutual funds outside of your retirement accounts that you want to dump, do so before Dec. 31.

You can use those losses to offset any taxable gains. If your losses exceed your gains, you can deduct up to $3,000 from your regular income.

If you plan to reinvest in another fund, call the fund and make sure it has already made its year-end capital-gains distribution. Otherwise, you'll owe taxes on those distributions even though you didn't receive them.

You can give up to $11,000 to anyone without incurring the gift tax. Together, a couple can give one person $22,000. To avoid the annual limit entirely, pay tuition or health-care bills directly.

Watch out. This may be the year the runaway alternative minimum tax hits you. You can't do much about but there's time for some planning.

Go to H&R Block's AMT Estimator to see whether you're at risk.

If you will owe the AMT in 2005 but not in 2006, you may want to wait until early next year to pay otherwise deductible bills that can't be claimed under the AMT, such as property taxes and state and local income taxes. While you pay taxes on more of your income under the AMT, the top rate is only 28 percent.