An overpayment claimed on a return may be applied as a credit for your next year's estimated tax or you may request that it be refunded to you. 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. Page provides taxpayers and tax professionals the mailing address for submitting Form 843. Get free tax help from the IRS. File your taxes, get help preparing your return, help yourself with our online tools, find your local office – or call us. 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. Cashing an erroneous refund check may result in interest due to the IRS.