USPS Default on Mandated $5.6 Billion Prefunded Payment: For the second time in two months, the U.S. Postal Service will not make a mandated payment to prefund retiree health benefits. Absent legislative action, the Postal Service is unable to make a scheduled $5.6 billion payment to the U.S. Treasury on Sept. 30. As was the case with the default of a similar $5.5 billion payment due August 1, customers can be confident in the continued regular operations of the Postal Service. We will continue to deliver the mail and pay our employees and suppliers