Maybe their tax payments got lost in the mail. 

The U.S. Postal Service turns out to have more tax delinquents in its ranks than any other federal agency or department, according to the Internal Revenue Service. 

IRS statistics from 2008 detailing the amount of money federal workers failed to pay the government in taxes showed postal service employees owed $297.93 million -- nearly 10 percent of the $3.04 billion owed by federal employees and retirees from dozens of agencies.

The tax gap among federal workers comes at a time when the federal government is running record deficits and trying to raise the $12 trillion debt limit so that it can continue spending at record levels next year. 

USPS spokesman Mark Saunders said in a written statement that it's "important" to consider that the percentage of those owing taxes at the postal service is "relatively small" compared with other agencies. The postal service is the largest federal employer outside the military, so it would predictably have a relatively large number of delinquents -- the actual percentage of those failing to pay taxes, 3.95 percent, was less than at a number of other agencies. 

But with $297 million in unpaid taxes, Saunders said the postal service is still trying to lick the problem. In Post Office terms, that kind of money could buy 677,122,172 stamps. 

"We urge our employees to comply with all tax laws and are encouraged that many who have been delinquent have agreed to payment plan with the IRS," Saunders said. Of the Postal Service's more than 732,000 employees, about 29,000 owed taxes. 

The data from late 2008 covered all agencies with more than 25 employees and mostly covered the 2007 tax year -- the most recently available data. It was not clear how much of the money has been repaid. The data showed just about every federal sector had tax evaders, but the problem was far worse in certain corners of the government. 

The military, between active duty personnel and reserves, accounted for $301 million of the total owed to the government. 

Military retirees accounted for another $1.34 billion. The only department that came anywhere close to the Postal Service's IRS bill was the Department of Veterans Affairs, which owed $131.29 million. 

That bill was $2.47 million for the U.S. Senate; $5.81 million for the House of Representatives; and about $813,000 for the Executive Office of the President. 

The Treasury Department owed $6.99 million. But the treasury actually boasted the best rate of all the departments, with only .98 percent of its employees labeled as tax delinquents. Inside the treasury, the IRS had a rate of .76 percent. Perhaps accounting for the low rate at the IRS is the fact that IRS employees can be fired for failing to pay taxes. 

The agency with the highest percentage was the National Capital Planning Commission, which had a rate of 10.42 percent.