If ever there was an area of taxation that needed simplification, it is the American corporate income tax. Companies end up filing tax returns containing thousands, or even tens of thousands, of pages.

In such length and complexity, opportunities lurk for any company that is willing to take aggressive tax positions. They might be virtually sure to lose if the Internal Revenue Service understood how something on Page 1,235 had interacted with something on Page 2,947 and challenged the result, but there is at least a reasonable chance the I.R.S. auditor would not figure it out.

“Today,” complained the I.R.S. commissioner, Douglas H. Shulman, in a recent speech, “we spend up to 25 percent of our time in a large corporate audit searching for issues rather than having a straightforward discussion with the taxpayer about the issues.”

To save that time, and to learn about things that are being missed, the I.R.S. is trying to require companies to give the agency a road map not only of the games that are being played, but of the maximum possible tax hit that companies would take if the I.R.S. chose to challenge them.