WASHINGTON — More than 3 million people will have to wait until February to get their tax refunds because of Congress' late fix to the alternative minimum tax, the IRS said yesterday.

Congress put a one-year freeze on growth of the alternative minimum tax last week, shielding many middle- and upper-middle-income taxpayers from first exposure to the tax. But Congress' late action means the Internal Revenue Service won't be able to start processing five AMT-related forms until February, delaying potential refunds for those people until that month.

Between 3 million and 4 million people filed in January of last year using those forms, with many of those people expecting a refund, the IRS said.

The average refund in 2007 was $2,324, the agency said.

As many as 13.5 million people will have to wait until Feb. 11 to start filing with the five AMT-related forms, but the IRS said filing patterns show only between 3 million to 4 million of those people file during the early tax season anyhow.

The IRS was able to reprogram its computers to begin accepting the seven other AMT-related forms when the tax season opens in early January.

But the tax packages that will start arriving in the mail beginning after New Year's Day were printed in November, before the AMT fixes were approved by Congress. The IRS has created a special section on its Web site, www.irs.gov, with updated copies of AMT forms.

The alternative minimum tax was passed in 1969 and was aimed at about 155 very wealthy families who used deductions to avoid paying any federal income tax. The AMT disallows certain deductions and credits. It was not adjusted for inflation; as a result, over the years it has hit a growing number of middle-income taxpayers.

More than 4 million were subject to it in the 2006 tax year. Without the congressional fix, more than 20 million families would have been faced with an extra $2,000 tax hit on average.

The five forms affected by the delay are: