The IRS has warned of serious problems for taxpayers, compounded as the delay worsens. Grassley made the following comment:

“This ping-pong game is just making the filing season a bigger fiasco by the day. Every day’s delay by House Democrats means hundreds of thousands more taxpayers will have hundreds of millions of dollars in refunds delayed. The House leaders needs to face the music and pass a clean AMT bill. I’m asking the GAO for an accounting of the impact of the delay on taxpayers so a few months from now, we’ll all understand the consequences of fooling around with the filing season.”

The Treasury had said that the failure to enact the AMT patch before November would affect the computation of various tax credits, such as the child tax credit, and the retirement savings contribution tax credit, meaning that an additional 25 million taxpayers would face delay in the processing of their returns and the payment of refunds.

"The failure of Congress to act in a timely manner in passing an AMT patch has raised great concerns in my mind about the extent taxpayers will be facing a filing fiasco early next year," Grassley wrote in his letter to David M. Walker, Comptroller General of the GAO.

According to Grassley, during the 2007 filing season, the IRS processed over 135 million income tax returns; issued over $233 billion in refunds to taxpayers; received nearly 70 million calls on its toll-free telephone lines; assisted about five million taxpayers at its walk-in and volunteer sites; and provided assistance to millions of taxpayers via the IRS website.