Federal workers and retirees owed more than $3.5 billion in unpaid taxes last year, a $200 million increase over the previous year, the IRS said Tuesday.

Almost 305,000 federal workers and retirees owed back taxes as of Sept. 30. That's down from 318,000 the year before.

The delinquency rate was 3.1 percent for the 9.8 million workers and retirees included in the data. That's down from 3.3 percent the previous year.

The IRS compiles data each year on unpaid taxes by federal workers. The data does not include workers who have enrolled in installment agreements to pay their back taxes.

Among executive departments, workers at the Department of Housing and Urban Development had the highest delinquency rate, at 4.7 percent. Workers at the Treasury Department, which includes the IRS, had the lowest delinquency rate, at 1.2 percent.

Tax compliance at the IRS is generally better than at other federal agencies in part because the IRS cannot share information about tax delinquents with other departments. A 1998 law calls for removing IRS employees who are found to have intentionally committed certain acts of misconduct, including willful failure to pay federal taxes.

"It is an honor and a privilege to serve in the federal workforce," said Rep Jason Chaffetz, R-Utah, chairman of the House Oversight Committee. "These employees are not exempt from their civic responsibility to fulfill tax obligations and those who refuse to pay what they owe should be held accountable."

The House Oversight Committee is scheduled to consider a bill Wednesday that would make someone with a "seriously delinquent tax debt" ineligible for federal employment.

Compared to the general public, federal workers are more likely to pay their federal taxes.

The IRS does not yet have data on the general public for 2014. But in previous years, the delinquency rate for the general public was between 8 percent and 9 percent — much higher than the rate for federal employees, the IRS said.

In Congress, House employees had a higher delinquency rate than Senate workers. About 5 percent of House employees owed back taxes, compared to just 3.5 percent of Senate workers.

Among active duty military, just 1.4 percent owed back taxes, the IRS said.