Why did I receive a letter 4883C?

The IRS Taxpayer Protection Program processes returns flagged as potential identity theft cases. When a return is flagged as a potential ID theft case, a Letter 4883C is sent to the address on the return requesting that the taxpayer call. When the taxpayer calls, the IRS customer service representatives go through a series of questions to determine the identity of the caller and confirm that the taxpayer filed the return in question. If the identity and return are verified, the return is forwarded for posting.