Taxpayers who use five forms related to the alternative minimum tax will have to wait an extra month before they're allowed to file so the Internal Revenue Service can reprogram computers, The Washington Post said.

The delay affects those filing for tax credits for education, residential energy use, child- and dependent-care expenses, mortgage interest and the purchase of a first home by residents of the District of Columbia. The IRS estimates that the change will affect up to 4 million taxpayers who typically file early.

"We regret the inconvenience the delay will mean for millions of early tax filers, especially those expecting a refund," acting IRS Commissioner Linda Stiff told the Post.

Congress approved the one-year change to the alternative minimum tax last week.