File a refund claim on Form 1040X if you want to take advantage of a retroactive change in the law, if you have overpaid your tax because you failed to take allowable deductions or credits, or overstated your income. You may use Form 1040X to correct your return if you underreported your income or improperly claimed deductions.
File a refund claim on time. The time limits discussed in 47.2 must be strictly observed; otherwise, even if you file a valid refund claim, it will be denied because of late filing.
You do not have to file a refund claim if you have overpaid your tax due to excessive withholding of taxes on your wages or salary, or if you have overpaid your estimated tax. You get a refund on these overpayments by filing your tax return and requesting a refund for these amounts. You must file your return within three years from the time the tax was paid to get the refund (47.2).
For a refund of an overpayment of FICA taxes, see 26.8for how to claim a refund on your tax return. If you are not required to file a tax return, you file a refund claim on Form 843.
If you are entitled to a refund due to the earned income credit ...