More than 15.4 million Americans soon could learn that what the tax man giveth, the tax man can take away.

Those people surprisingly could owe taxes for 2009 because of complications in the Making Work Pay tax credit, a cornerstone of the $787-billion economic stimulus package enacted in February, according to a government watchdog report released Monday.

More than 1.2 million of them could face Internal Revenue Service penalties, at least technically.

"It definitely is going to be a surprise to some taxpayers, who are either going to have a balance due or a reduced refund this year,"