Thousands of owners of closely held businesses who have made contributions to so-called super individual retirement accounts may be in for a rude shock from the Internal Revenue Service.

Super IRAs allow people to earn higher-than-market interest rates on their retirement savings, but only if they maintain a second account with the same bank or savings and loan association. That other account yields little interest.

These arrangements pay off for everyone involved -- except the IRS. Business owners shift interest income from their companies to tax-deferred retirement accounts, and savings institutions attract two new accounts for the price of a single IRA marketing campaign.

The word is out, though, that the IRS may snuff out super IRAs, as early as this month, by declaring that the extra interest that these accounts earn qualifies as excess contributions to the IRA account. That means the extra interest would be subject to individual income taxes, plus a 10% premature distribution penalty and a 6% excess contribution tax.

And that is just part of the problem. "How does a [taxpayer] determine excess interest?" asks Rhonda L. Davis, a supervisor in the national tax department of Ernst & Whinney, in Washington, D.C. "Do you look at interest rates in a given town, or in the country as a whole? I doubt that the IRS will tell us."

The big worry for people with super IRAs however, is whether the IRS will make its ruling retroactive to accounts established prior to this tax year. Neither Davis nor Kim B. Gates of the U.S. League of Savings Institutions, a 3,500-member organization based in Chicago, is willing to speculate. The IRS is also remaining mum on the subject. "We're working on something," says Wilson Fadely, an IRS spokesman in Washington, D.C., "but we don't like to speculate in advance on what it will say."