CP268 tells you we made changes to your return because we believe there is a miscalculation on your return. You can get in-person help at your local IRS Taxpayer Assistance Center.Call for an appointment after you find a Taxpayer Assistance Center near you. The underpayment interest applies even if you file an extension. If you pay more tax than you owe, we pay interest on the overpayment amount. Get your refund status. You can find the CP or LTR number on the right corner of the letter. Basically, if he repays gross (even pro-rated gross) in the current year, you can simply reverse the amount using the same pay code, which will reset the taxes. This notice is issued annually to remind you of your Tax, Penalty, and Interest balance that has been in "currently not collectible" (CNC) status. Attach IRS form 12661.