IRS officials say they're trying to close that gap, but it isn't easy.

"People should be able to rely on the information they get from us," said Marilyn Soulsburg, acting IRS commissioner for customer service. But for sticky problems, she added, "oftentimes the taxpayers' best bet is to seek professional advice."

A little more than half of American taxpayers had their returns professionally prepared last year, according to the IRS. Others are increasingly turning to computer tax software programs, which are modified each year to reflect changes in the tax code and "ask" people detailed questions about their finances.

The IRS estimates that only 1 percent of returns done electronically contain errors, compared with 20 percent of those prepared on paper.

But millions of Americans still do their taxes with nothing more than a pencil, a calculator and a pot of coffee. If they get stumped, the IRS offers a variety of toll-free telephone lines to get answers.

The IRS employs about 7,000 people in its toll-free telephone program, which expanded its 15,000 lines for the first time this year to seven days a week, 24 hours a day. Last year, almost 70 million callers phoned the IRS for tax advice or to inquire about their accounts.

Dave Medick, national director of the IRS telephone service, said the agency's monitoring of calls indicates that last year's answers were accurate 85 percent of the time regarding tax law. For questions about individual taxpayer accounts, the accuracy rate was 90 percent.

As recently as 1995, the accuracy rate for both types of questions was placed at about 90 percent, but IRS recently switched to a centralized call monitoring system to replace the spot test calls made in the past.

"We are always working to improve," Medick said. "We have instant replay, so to speak, in the areas where we have the most difficulty."

That "replay" includes bulletins sent to the 25 IRS phone service locations detailing areas of tax law where errors are more frequent. The IRS also has redoubled its training, but the expansion to a 24-hour system without additional staff has put a strain on the quality of its advice.

"We have the same group of people working more hours, so we don't have the same skill base," Soulsburg said.

But the IRS isn't too sympathetic toward people who claim they made a mistake because of bad advice.

"For the most part, the responsibility still lies with the taxpayer to file an accurate return," Soulsburg said. "That's why there's a bigger burden on us to make sure our quality is as high as it can be."

Still, although the taxpayer is ultimately responsible for all taxes, the IRS will forgive penalties if the problem is caused by the agency's advice. Taxpayers who believe they were given bad guidance should contact the IRS to have any penalty deleted. It's a good idea for the questioner to record the name of the person providing the advice and the time and date of the call.

Another problem IRS has been working to overcome is the number of times taxpayers simply can't get through at all. A recent General Accounting Office report found that only about 51 percent of all calls were answered in 1997, and that was up 20 percent from the year before.

Last year, the agency expanded from typical business hours to 16 hours a day, seven days a week, and this year calls are answered round-the-clock all week during tax-filing season, from the beginning of January through mid-April.

"We've given people more opportunities to get through at different times," Soulsburg said.

Another free option for taxpayers with computers is the IRS site on the Internet — www.irs.ustreas.gov — that includes thousands of pages of tax publications and forms. The site, visited more than 340 million times in fiscal 1998, provides answers to frequently asked questions and features alerts to any widespread tax problems.

There are other alternatives. IRS tax help, including face-to-face contact, is available at 400 agency offices around the country, with 250 open Monday through Saturday through April 10. Taxpayers should call the IRS for more information.