You get an overpayment credit when your tax payments exceed what you owe. You'll automatically receive a refund of the credit.CP268 tells you we made changes to your return because we believe there is a miscalculation on your return. You can find the CP or LTR number on the right corner of the letter. There are no refund claims based on "Net Operating Loss Carryback". A paid tax return preparer who files Form 843 for you must sign the form and fill in the identifying information at the bottom of the form. Let the IRS know of a disputed notice. The IRS may apply the amount of any overpayment against any federal tax liability of the person who made the overpayment, IRC 6402(a). You can request a replacement check. Call the Customer Service Center at 609-292-6400 and speak to a Division Representative.