The IRS knows that sometimes things happen, and taxpayers don't always file their income taxes correctly. Forgetting supplemental or supporting documents, such as a W-2, is actually not that uncommon. If you find yourself in this position, don't worry. When you forget to submit any required forms along with your taxes, the IRS will definitely let you know what your next steps need to be, if any, in order to rectify the situation.
Do I Need To File an Amended Return?
If you file your taxes and realize you have forgotten to attach your W-2, then chances are won't need to file an amended return for this oversight. If you included all your income reported on your W-2 when you originally filed your return, you won't need to file an amended return, because the information you reported was accurate. You will still receive your refund, even if you did not attach your W-2, if you are owed one.
However, if you notice some discrepancies that cause you to owe additional taxes, you may have to file an amended return, and possibly may be subject to late-filing penalties or fees if you pay them after April 15th. Either way, when the IRS catches this error, you will receive a letter instructing you how to proceed.
Filing an Amended Return
According to the IRS, you need to file an amended return only to make changes to your number of dependents, filing status or total income reported. You do not need to file an amended return if you have only made some mathematical miscalculations, as the IRS will make these corrections for you. However, in the event you receive a notice from the IRS instructing you to file an amended return, then you need to do so as soon as possible. To file an amended return, use IRS Form 1040X, Amended U.S. Individual Income Tax Return.
You cannot file Form 1040X electronically. If you e-filed your original return, you must return your necessary documents along with a paper-amended return to the IRS. If the amended return results in the IRS owing you a refund, you have up to three years to file it to receive the monies owed to you.