The United States Postal Service has lost $51.7 billion between 2007 and 2014 and has not earned a profit since 2006, according to a report from the Tax Foundation.

"There is no turnaround in sight," states the report. "The Postal Service will almost certainly register another multibillion dollar loss in 2015; for the first two quarters of 2015, it suffered a net loss of $2.8 billion."

In addition, the report finds that USPS has failed to make legally required payments to the U.S. Treasury and will default on its statutory obligations, which include the Postal Service Retiree Health Benefit Fund.

"Although the Postal Service has not yet received an explicit taxpayer bailout, it has failed to meet its legal obligations for several years in a row," the report states. "The odds that a bailout will eventually become unavoidable increase as the sea of red ink continues rising."

The Government Accountability Office (GAO) estimates that the Postal Service's unfunded liabilities grew 62 percent from 2007 to 2013. The Tax Foundation says it is doubtful that the Postal Service will be able to meet its obligations.