NEW YORK (CNNMoney.com) - Did you pay too much in taxes last year? Millions of Americans did last year, according to a government report.

In today's top 5 Tips we're going to give you the heads-up on some commonly missed tax deductions.

Over 2 million tax filers overpaid about $438 per return in 2002, according to the most recent stats from the Government Accountability Office. And over one million filers in 2004 missed taking advantage of a tax break that would allow them to deduct sales tax instead of state income tax. Why? The change to the tax law was enacted late in the year and people weren't prepared for it.

Last minute changes to the tax laws are actually quite common, according to the IRS. In 2001 alone there were 440 code changes. And while the IRS sends tax forms out in late December, be aware that there could still be many changes in the pipeline.

This year you'll be able to get tax credits of up to $3,400 if you buy one of the first 60,000 hybrids available by the manufacturer. If you're still fence-sitting about investing in a hybrid, you're better off getting on a waiting list now. The credit will be phased out for vehicles offered by a given manufacturer once that company has sold 60,000 hybrid cars.

If you've given to charity, make sure you're specific about when you gave money. Typically you are allowed to deduct cash donations of up to 50 percent of your adjusted gross income.

But if you gave money between August 28th and December 31st, you will be able to claim deductions of up to 100 percent on your cash donations. Plus, if you used your car for business purposes between Sept. 1st and Dec. 31st, you'll also be able to deduct up to $.48 and a half cents from your mileage costs because the government factored in the higher cost of fuel around this time. Before September 1st, you could only deduct up to $.40 and a half cents.

This is a great option for older people on a limited income who have a lot of medical expenses. While the hurdle is high -- your medical expenses must be more than 7.5 percent of your adjusted gross income -- there many deductions that people often miss, according to Greg Rosica of Ernst and Young.

You can deduct the cost of items like contact lenses, eyeglasses, and hearing aids. Doctor co-payments don't count, unfortunately. But generally anything a doctor prescribes, like a humidifier, support hose, a pool for therapeutic purposes, costs associated with a seeing eye dog -- even the cost of driving to the doctor can be deducted, according to Donna LeValley of J.K. Lasser's "Your Income Tax 2006." And don't forget, people who have diagnosed problems, like hypertension or obesity can deduct out-of-pocket costs of weight-loss programs.

If you or your siblings support elderly parents, you'll be able to claim them as dependents, even if they live by themselves or in a nursing home. There are some caveats. Mom or dad can't be making more than $3,200 a year, but that doesn't include social security income. If you have a lot of brothers and sisters, you'll all be able to take turns getting the deduction.

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Gerri Willis is a personal finance editor for CNN Business News and the host for Open House. E-mail comments to 5tips@cnn.com.