The tax credit for corporate research and 54 other breaks in the U.S. tax code expired Dec. 31. They've been replaced by confusion and frustration.

As U.S. corporations such as Intel Corp. and General Electric Co. report earnings this month, they're warning shareholders and analysts that they can't assume Congress will reinstate lapsed breaks retroactively, though lawmakers have done just that four times in the past eight years.

Corporations say they're unable to offer analysts and investors consistency in predicting what their tax rate will be in any given year and must explain fluctuations that can cause profit to vary by hundreds of millions of dollars.