The U.S. Postal Service is seeking to increase the price of its first-class mail forever stamp in the biggest price hike since 1991.

Priority flat rate prices could also increase by an average of 5.9 percent.  For example, a medium flat rate box that now goes for $13.65 would increase to $14.35.

According to USA Today, the Postal Regulatory Commission must approve the changes before they could go into effect.

The new price plan comes at a time when USPS is struggling with sales, as mail has been replaced with electronic communication.