When you file a tax return and you claim that the IRS owes you money, that is called a claim for refund. The IRS uses letter 105c to deny a claim for refund. The usual reason for denying a claim is because it was not filed within the three-year time limit. Although the IRS will not return your money, they will agree that you don't owe them any money for that year. However, you don't get an offset for any other tax debt you may owe. If you don't have a valid claim, don't waste your time with IRS appeals. But if you do have a valid claim, you may pursue your case with IRS appeals or in US District Court. Either of these two options may be fully explored with a confidential tax law attorney.