Deficit cutters struggling to make ends meet in Washington are eyeballing an unusual pot of potential revenue: back taxes owed to the government by federal employees themselves.

According to an IRS study last year, those employees and federal retirees owed a staggering $3.3 billion dollars in delinquent tax payments to the government.

The federal agency with the largest back-tax bill? The US Postal Service, where hundreds of thousands of employees owed a total of more than $283 million, said the report.

Also high on the list is the Department of Veterans Affairs, where employees had more than $156 million in back taxes.

The biggest group, though, is retired military personnel. That group owed more than $1.5 billion dollars.

And even the White House folks are behind in their taxes. Employees in the executive office of the president, which includes nearly 2,000 employees, owed more than $831,000 to Uncle Sam, the IRS found.