The IRS was unable to apply the taxpayer's overpayment to the following year's taxes as requested on the return. This could be caused by an adjustment to the filed return or the IRS record of payments made did not match the payments claimed on the return. The notice could also be generated if the IRS offset the refund against other taxes owed or other debts outstanding which are legally collectible through the IRS offset program.
Sections of the Notice:
Sample CP 45: PDF Page 1
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.