Back in 1997, Congress repealed the alternative minimum tax for corporations with average annual gross receipts of $5 million or less. But some businesses mistakenly continued to pay the tax -- to the tune of $37 million. So, in 2001, the IRS mailed roughly 9,500 notices to companies that may deserve a refund. A nice gesture -- but the tax inspector general recently discovered that more than a third of the companies didn't receive notices. In a letter to the IRS commissioner, Republican Sens. Olympia Snowe of Maine and Christopher Bond of Missouri asked for the matter to be resolved, noting that the oversight probably prevented companies from buying equipment or hiring staff. Tax professionals who spoke with Inc. agreed that, while the IRS is partly to blame, a decent tax preparer wouldn't have missed the AMT's repeal. "If one of my clients paid that tax erroneously, I'd be very upset," says Roy Quick, a St. Louis tax agent.