The early results are in: About 15 percent of taxpayers trying to claim last year’s tax rebate on their returns have made mistakes.

According to the IRS, some people are claiming the rebate when they don’t deserve it. Others claim the wrong amount. And some erroneously put the amount they received last year on the “recovery rebate credit line.”

Mistakes can delay refunds.

Last year’s economic stimulus check was a 2008 tax credit. But to get money as fast possible into the hands of consumers, the checks were sent out based on information on 2007 returns. Rebates for individuals ranged from $300 to $600, and married joint filers got double that amount. Plus, parents with younger children could receive $300 for each child.

Your 2007 information, though, may have made you ineligible for a rebate or you might have gotten less than the maximum amount. And if your situation changed in 2008, you might be able to claim the rebate on this season’s tax return.

You will need to know how much of a rebate, if any, that you got last year to figure out how much to claim now.

If you forgot, check the notice the IRS mailed to you last year. Or, go to the IRS Web site and check out How Much Was My Stimulus Payment. Or, call the IRS at 866-234-2942.

Computer software will automatically figure and report the amount of your rebate recovery credit.

If you’re the old-fashioned type and filing a paper return, use the work sheet in the 1040 instruction booklet to figure your credit. Then report the number on Line 70 of the Form 1040; Line 42 on Form 1040A and Line 9 of the 1040 EZ form.

You can also enter zero on the line and let the IRS figure out your rebate credit.

One other important point: Remember, last year's stimulus check does NOT have to be reported as income on your tax return.