The Internal Revenue Service's taxpayer assistance program gave wrong answers one-third of the time last week to questions posed by a Washington Post reporter to 11 IRS offices here and around the nation.

Of 110 questions phoned to IRS tax assistance workers by an individual seeking help preparing a tax return, 37 answers were wrong. The average was slightly better for the Washington area, where 12 of 40 answers were wrong.

"It disturbs me . . . but it does not surprise me that we give wrong answers," said Stanley Goldberg, director of the IRS taxpayer service division.

He said errors are the result of human failing and "very complex tax laws."

Goldberg said that a survey conducted by IRS in January found that the telephone service's answers were wrong only 3.1 percent of the time. In that survey, IRS agents monitored 40,000 telephone calls to its offices to determine the accuracy of employe's answers.

Two years ago, the General Accounting Office surveyed the IRS taxpayer service and found it was wrong 13 percent of the time.

"But we could be 99.9 percent accurate and we still would be concerned about the accuracy of that one-tenth of 1 percent," said Goldberg.

Post survey questions that drew the most wrong answers included this one:

"Last year, I brought a $100 calculator and use it at work. Can I deduct that as a business expense?"

Two offices -- Miami and New York -- said no. Two others -- Houston and Los Angeles -- said maybe, depending on whether the taxpayer was required by his employer to have a calculator. The other seven offices -- including those serving in Washington area -- said yes, but then suggested a variety of deductions ranging from as little as $20 to as much as $100.

None of the answers was completely correct.

Asked to provide the correct answer to the calculator question, officials at IRS headquarters at first said it could be deducted only if the taxpayer's employer required him to have one. But within an hour, the same officials reversed themselves.

"It does not have to be required," said Scott D. Waffle, chief of media relations. "If it is ordinary and necessary for work, it can be deducted," he said.

Waffle said the amount of the deduction would depend on the depreciation schedule, or estimated life of the calculator, and whether the taxpayer claims an investment credit. A $100 calculator purchased last year with an expected life of five years translates into a $26.67 deduction, including $20 for the depreciated value and $6.67 for the investment credit, he said.

One final twist: If the calculator is used 50 percent of the time for business and 50 percent for personal reasons, the $26.67 deduction shrinks to $13.34, IRS said.

Taxpayers who make mistakes because IRS gave them the wrong answer stand to lose money in two ways. First, they may overpay their tax if they fail to take a legitimate deduction. And second, if the deduction they take isn't legitimate, they will have to pay the difference if they are audited and the error is discovered. In addition, they could be charged interest on tax owed as a result of the error.

"The taxpayer is totally responsible for his return," Goldberg said.

One exception is when an IRS employe actually prepares the return for a taxpayer and makes a math error. In that case, the taxpayer must pay the difference in tax but is not charged interest on the difference.

During the peak filing season last year, from Jan. 1 to April 15, the IRS's telephone program fielded 19 million calls, about 1.1 million of them from Virginia, Maryland and the District of Columbia.

This year IRS has assigned 6,000 employes to answer telephones during the busiest times. The Virginia offices have 80 workers at peak hours, and a total of 90 people work in the offices serving Maryland and the District.

Goldberg said none of them are "temporary" workers. "These are not folks we brought in off the street to answer telephones," he said.

Instead, he described the IRS taxpayer crew as a mix of experienced full-timers and trained "seasonal" workers. About 37 percent of the tax helpers are full-time IRS employes, Goldberg said.

The other 63 percent are the seasonal employes who work for IRS during the current tax filing period and during summer vacations when regular IRS workers take their vacations.

Training for seasonal employes is the same as for full-time regular workers, Goldberg said. That includes a four-week classroom course on tax law and one week of on-the-job experience, he said.

In addition, he said, IRS routinely monitors calls to determine if employes are answering questions correctly. Also, seasonal workers are instructed to refer complicated calls to more experienced technical employes.

"We hire the brightest people we can and train them and supervise them," he said.

But despite all that, some employes "try to overreach . . . try to overserve . . . and go beyond their training," he said. They also may fail, in some cases to probe deeply enough into the situation before giving answers, he said.

Goldberg said that taxpayers who discover that IRS sometimes give wrong answers shouldn't stop asking for information.

"The vast majority get correct answers," he said.

But, he suggested, taxpayers who are not satisfied with the answer they get from an IRS taxpayer helper should call a second time and ask the question again. "If the second answer is inconsistent with the first, call and say you got two answers and ask which is correct," he said.

In the questions submitted by the Post, IRS answers were most often correct on those involving employe travel expenses, charitable contributions and the costs incurred when buying a home.

Here is a summary of some questions and the answers that were provided:

I want to deduct child care expense for a 10-year-old. I have a full-time housekeeper who cooks, cleans and looks after my daughter when she is there after school. Is the housekeeper's salary deductible?

Six of the offices, including Washington, said the taxpayer must prorate a full-time housekeeper's salary to determine the amount of time devoted to child care. That is wrong, according to the national IRS office. A taxpayer can consider all of the full-time housekeeper's salary in computing the child care credit.

Last winter I bought cauiking for my house as an energy conservation step. I also bought plastic sheeting to tape over jalousie windows. Is the cost of caulk tape and plastic sheeting deductible?

Seven of the offices including those in Washington and Richmond gave the wrong answers to this question. This District said chaulking costs do not qualify; Richmond said all insulation material qualifies.

But national IRS officials said the caulking purchase would count toward computing the energy credit, on homes completed prior to April 20, 1977, while plastic sheeting and tape would not.

My sister is a widow with three dependent children who receive Social Security benefits. We don't think she can claim them as dependents (because they receive Social Security payments). Is there any way she can qualify as head of household, since they do live with her?

Seven offices, including those in the District, Baltimore and Richmond, provided incorrect answers. National IRS said that the mother could qualify as head of the household so long as she provided 50 percent of the cost of running the household. She need not provide 50 percent of the cost of food and clothing and other support for the children, in order to meet the 50 percent test on household costs, IRS said.