More than half a million current and former federal employees owe $6.3 billion in unpaid federal taxes, prompting House Oversight Committee Chairman James Comer, R-Ky., to demand answers from the IRS about why existing enforcement tools have not been used more aggressively.

In a letter Thursday to IRS CEO Frank J. Bisignano, Comer requested records detailing the agency's efforts to collect unpaid taxes from federal workers and retirees, including whether it has used wage garnishments and pension levies authorized under federal law.

The inquiry follows a Treasury Inspector General for Tax Administration report showing tax delinquency among federal employees has continued to climb despite repeated IRS collection efforts.

According to the report, more than 571,000 current and retired federal employees owe a combined $6.3 billion in back taxes. The number of delinquent federal workers has surged 43% since 2021, while 215,000 current employees — nearly 7% of the federal workforce — were behind on their federal tax obligations in 2024.

The watchdog also found roughly 50,000 current and former federal employees failed to file tax returns. Among them were 14,000 repeat non-filers earning at least $100,000 a year, and 122 federal workers who had gone eight years or more without filing. About one-third of all non-filers worked for the U.S. Postal Service.

Comer said the findings show the federal government must do more to enforce tax laws within its own workforce.

"With TIGTA's report showing continuous increases in tax noncompliance among current and former federal employees, the Committee is concerned that this trend will continue unless IRS, the Executive Branch and Congress act now to proactively curb noncompliance with federal tax laws," he wrote.

The report also highlighted the limited success of the IRS' voluntary compliance efforts.

Last summer, the agency mailed 427,000 delinquency notices to federal employees and retirees urging them to resolve their tax debts. Within a month, about 59,000 recipients made a payment, but only 4,700 paid their balances in full.

In all, the IRS recovered just $58 million — less than 1% of the $6.3 billion owed.

"This data demonstrates that the majority of noncompliant federal employees ignored the IRS letters and failed to resolve their tax liabilities in a timely manner or at all," Comer wrote.

The congressman is asking the IRS to disclose how often it has used the Federal Payment Levy Program, which allows the agency to garnish up to 15% of federal salaries and retirement benefits to collect unpaid taxes. He requested the records by July 9.

The watchdog noted the Treasury Department has a relatively low tax delinquency rate of 2.4%, likely because it can hold its own employees accountable. Other federal agencies generally cannot access IRS tax information, which Comer argued creates a loophole that weakens enforcement.

"It seems unlikely that employees who are already failing to pay or to file taxes for years in violation of federal laws would voluntarily identify themselves to their employing agencies," Comer said.