The entire membership of the Washington Teachers' Union was overcharged in dues by an amount totaling more $700,000, a discovery that ultimately led to last month's resignation of the group's president, officials with the union and its parent organization said this week.

Each of the union's roughly 5,000 members was overcharged $144 this summer in a monthly payroll deduction, but only about a third of the teachers have been reimbursed so far, officials said.

After one member complained to the American Federation of Teachers, the parent body sent in an accountant who discovered other financial improprieties, which led to an independent audit of the union's records. The union's executive board then demanded that President Barbara Bullock step aside, and it also asked for the resignations of Treasurer James Baxter; Bullock's chief assistant, Gwen Hemphill; and Bullock's driver.

The U.S. attorney's office is conducting an investigation, and union officials are awaiting results of another audit of the union's finances. Federation spokesman Alex Wohl said that audit is nearly finished.

Wohl said that reimbursing teachers for the overcharges is taking time because a new system of check writing and bill paying had to be created after the earlier audit raised concerns about a number of undocumented checks and questionable use of business credit cards.

"We should have it done quickly now," he said of the reimbursements.

But several teachers, speaking on the condition they not be named, said this week that union officials have not responded to their phone calls seeking reimbursement. And they complained that the union has applied the overcharge to future dues payments rather than repaying it outright.

In an Oct. 28 letter, interim union President Esther S. Hankerson urged union members not to talk to the news media about the financial problems and said they should instead direct reporters to her or the federation. Hankerson has not returned more than a dozen calls to her office by reporters, and someone who answered Hankerson's cell phone this week told a reporter that she had the wrong number.

Bullock, who had been president since 1993, reached by phone, declined to comment. She also declined to provide the name of her attorney.

The one-time dues overcharge occurred after the union successfully won a new contract for D.C. public school teachers that included a retroactive pay raise. Union members pay $24.75 in dues every two weeks, while nonunion employees who benefit from the union's bargaining with the school system pay 85 percent of that amount, or $21.04, a payment known as an "agency fee."

The dues and fees go up whenever teachers get a pay increase, so the union assessed a retroactive charge of about $16 per employee. But $160 was deducted from paychecks instead.

Officials gave varying estimates yesterday on the union's membership, but Washington Teachers' Union officials agreed that between 5,000 and 5,500 people were affected by the $144 overcharge, meaning that the amount involved is between $720,000 and $792,000.

Under federation rules, the union is supposed to conduct an internal audit every two years. The last time it did so was in 1995, Wohl said.

He said the federation had repeatedly asked for an audit. On at least one occasion, he said, the union said the delay resulted from a new auditor being hired.

"They said, 'It's coming,' " Wohl said. "We were assured that it would be there."

But it never came, and the federation took no action against the Washington union. Wohl said the parent body had a "working relationship" with its local affiliate and believed the audit would be completed.

He said the only step the federation could have taken would have been to sever its ties to the union, but there did not appear to be a reason for that.

He also said the Washington Teachers' Union fell behind in its dues payments to the federation earlier this year and that a payment plan had to be established to obtain back dues. Wohl said the Washington union eventually caught up in its payments, but he could not explain why it fell behind.