If you itemize your federal income-tax deductions, don't use the Pennsylvania state tax form 1099 you received this week.

It's wrong.

The red-faced state Revenue Department says it cannot explain how, but a computer tape from the wrong year was used to prepare and mail 900,000 forms detailing state tax refunds. The forms reported refund data from 2005 instead of 2006, said Steve Kniley, the Revenue Department's press secretary.

Then the state sent the faulty information to the federal Internal Revenue Service.

Kniley said he believed the state caught the error before the erroneous data were fed into Uncle Sam's computers.

"We're working overtime to mail corrected forms" to taxpayers, he said. "They will be marked 'corrected' in red letters."

The 1099 form is used by an estimated 300,000 Pennsylvanians who itemize deductions on their federal tax forms. If you deduct state taxes on your federal return, you must report any refund as taxable income the following year.

"We don't know how it happened. We made a mistake, and we feel bad about it. We're working hard to fix it," Kniley said.

The goof came to light when people noticed they were being listed as having received a refund last year when they recalled having to pay.

Contact staff writer Henry J. Holcomb at 215-854-2614 or hholcomb@phillynews.com.