This post is by Laura Saunders of The Wall Street Journal.

A pair of changes for 2011 could mean big headaches for taxpayers who report business or partnership income on their individual tax returns.

Both changes involve so-called 1099 forms, which are reports submitted to the Internal Revenue Service so the agency can cross-check information from different taxpayers.

The first change is momentous: It requires third parties -- credit- and debit-card issuers, PayPal and the like -- to tell the IRS about their payments to businesses. For 2011 and after, these firms must issue 1099-K forms to the IRS and the taxpayer giving the amount of such payments.

Why does that matter? This information can help the IRS flush out unreported income by small businesses. Cheating and mistakes cost Uncle Sam $122 billion a year, the IRS estimates, making it the largest single element of the $385 billion in annual unpaid taxes, known as the tax gap.

The new third-party payment information cuts two ways. It can help the IRS identify companies, such as online merchants, who aren't reporting income at all. But it also can shine a light on businesses that are underreporting their income, such as a restaurant that does a big cash business but declares income equal only to its credit- and debit-card payments.

There is some good news on the 1099-K front: After an outcry by the National Federation of Independent Businesses, or NFIB, and other groups, the IRS recently decided to drop plans to have businesses break out 1099-K receipts on their tax forms. Doing so would have imposed a huge burden, says Chris Walters, an official with NFIB, because it involved an onerous reconciliation process.

"Grocery stores would have had to show that $15 of a shopper's $40 debit charge was for food and the rest was a cash withdrawal, or else the IRS might think they're underreporting income," he explains.

But business owners shouldn't be lulled into a false sense of security. While they won't have to report the information on their returns, third parties must still provide 1099-Ks, and the IRS can still use those data in audits.

"Firms that might be 'outed' by this form should remember it's very much alive," says Don Williamson, a tax preparer who heads the Kogod Tax Center at American University.

The other potential trap: two new lines on several forms, including Schedule C (for sole proprietorships), Schedule E (landlords), 1120S (Subchapter S corporations) and 1065 (partnerships).

Those lines ask: "Did you make any payments in 2011 that would require you to file Form(s) 1099?" and "If 'Yes,' did you or will you file all the required Forms 1099?"

These simple-seeming questions could cause large penalties for some taxpayers.

Here is why: Firms usually are required to issue 1099 forms to providers of more than $600 worth of services during the year, unless the vendors are incorporated. That could include, for example, an accountant, a plumber, a website designer or a consultant.

In 2010, Congress stiffened penalties on taxpayers who neglect to provide 1099 forms. The higher penalties took effect in 2011, and now the penalty for nonfiling is $100 per violation -- $200, in most cases, because two forms are due, one to the IRS and one to the provider. The penalty for "intentional failure to file" is $250.

Williamson recalls one case in which penalties for multiple vendors and multiple years amounted to $35,000, even though nothing else on the return was disallowed.

By asking the two questions prominently on the return, the IRS is both reminding taxpayers of their obligations and setting a snare for scofflaws. If a taxpayer answers "no" and an audit shows he should have sent the forms, the answers could be evidence in favor of higher penalties. So "he's hoisted on his own petard," Williamson says.

In extreme cases, he adds, it would be easier for the IRS to allege civil fraud, because the taxpayer's answer is evidence that he or she was willfully noncompliant.

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