Is Your Tax Prepayer Qualified To File Your Return?

The experts entrusted with preparing the taxes for millions of Americans may sometimes actually create more problems with the IRS for their customers.

As part of a new government report, undercover investigators posed as customers at several of the nation's largest tax-return preparers. And, according to congressional sources, they found "a shocking lack of knowledge about very basic tax issues … bad advice that could get taxpayers in major trouble with the IRS."

The 1.5 million words in the Internal Revenue Code can at times confound even the most highly trained accountants. But employees at the three largest tax-prep companies can begin dispensing advice after just six to 11 weeks of training, and only Oregon and California require preparers to pass a state test.

"As it stands now, there is more testing for a plumber or a person who cuts your hair or who changes locks than for someone who files your tax return," said Nina Olson of National Taxpayer Advocate.

'We Expect Mistakes'

Legislation pending in Congress would require anyone who prepares returns for a fee to register with the IRS, pass an entry test and take brush-up courses.

Sen. Charles Grassley, R-Iowa, said, "You've got to be able to trust these people who are being paid to do your taxes."

John Hewitt, CEO of Liberty Tax Service, said mistakes are inevitable with something as complicated as tax documents, so customers should check the preparer's work. "We wouldn't be human if we were perfect," Hewitt said, "so we expect mistakes to be made. But we expect to correct it and do what's right for the customer each and every time."

The report comes at the height of what's already been a tough tax season for one tax preparer, H&R Block. The company was forced to admit to errors in its own corporate taxes, then it was accused of deceptive marketing practices in two major lawsuits.

For those thinking of turning to the IRS for free help instead, that could be just as risky. Government data show that even the agency that collects your taxes gives the wrong advice more than a third of the time.

ABC News' Nancy Weiner reported this story for "World News Tonight."