IMPORTANT:
"Approximately 4,000 plan sponsors received erroneous CP 283C, Notice of Balance Due for Incomplete/Late Penalties for their Form 8955-SSA, Annual Registration Statement Identifying Separated Participants with Deferred Vested Benefits. These erroneous notices were dated between July 28 – August 26, 2013."
For more information: http://www.irs.gov/Retirement-Plans/Form-8955-SSA-Penalties-Assessed-in-Error