Call it the stealth tax, the one that catches you by surprise as you're completing your tax return.

Call it the stealth tax, the one that catches you by surprise as you're completing your tax return.

The Alternative Minimum Tax was designed to ensure that all Americans were paying some taxes, especially those wealthy folks who seemed to be escaping them altogether. Problem was, middle- and upper middle-class taxpayers were the ones getting hit by it, especially as incomes and inflation rose.

To help soften the blow, Congress has put in place a series of patches to account for inflation, raising the exemption level for the AMT.

The 2008 patch was included in legislation designed to rescue the nation's financial system. It raises the AMT exemption for married couples filing jointly to $69,950, for single filers or heads of households to $46,200, and for married people filing separately to $34,975.

Without the patch, the exemption for taxpayers would have reverted to pre-2001 rates: $45,000 for married filing jointly, $33,750 in 2009 for individual filers.

If Congress hadn't added the 2008 patch to the $700 billion financial bailout package, some 26 million taxpayers would see their tax bills increase by an average of $2,200, President Bush said in October.

There are a few other new wrinkles this year, notes Mark Luscombe, principal analyst for CCH's tax and accounting group. There's some additional relief for people who were caught by the AMT as a result of incentive stock options, especially those who received the options during the high tech bubble of the early 2000s.

In essence, the AMT doesn't allow for certain deductions and credits. Among them: additional personal exemptions, itemized deductions for state and local taxes, some interest payments, most miscellaneous deductions and some medical expenses.

Some people have pushed for a repeal of the AMT.

"It never did serve its purpose of catching taxes from the wealthy filers," said Bob Meighan, vice president for the Consumer Tax Group of Intuit, Inc., publisher of the tax-preparation software TurboTax.

But don't look for the AMT to disappear during the Obama administration. Doing away with it would reduce revenues coming in to the U.S. Treasury at a time of record deficits.

During the presidential campaign, Barack Obama said he would continue to adjust the current patch for inflation so that the AMT did not hit additional middle class families.

Information about the AMT and how to file is included in IRS Form 6251. Tax-preparation software programs will do the calculations for you.