The U.S. Postal Service is so low on cash that it may have to shut down entirely this winter—unless Congress gives it a cash injection. The USPS will not be able to make a $5.5 billion payment due this month as it struggles to erase its deficit, which will hit $9.2 billion this year. “Our situation is extremely serious,” the postmaster general, Patrick R. Donahoe, tells The New York Times. “If Congress doesn’t act, we will default.” U.S. law forbids the USPS to take many of the steps it could to better its finances, like raising rates or selling things other than mail services. Donahoe is pushing major changes to help save money, including eliminating Saturday delivery, closing 3,700 post offices, and laying off 120,000 workers.