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.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. Use Form 843 to claim a refund or request an abatement of certain taxes, interest, penalties, fees, and additions to tax. A claim for refund is a request for reimbursement of amounts previously paid. Generally, if you have paid your balance in full you will file a formal claim. Get your refund status. This section provides for a refund of overpayment when the refund claim has been filed within a period of one year from the date of the claimed overpayment. Page provides taxpayers and tax professionals the mailing address for submitting Form 843.