If you discover an error on your federal income tax return after you e-filed or mailed it, you may want or need to amend your return. Perhaps you are eligible for a deduction or credit and you missed it the first time?

Here are eight key points the IRS wants you to know about when considering whether to file an amended federal income tax return.

1. Use Form 1040X, Amended U.S. Individual Income Tax Return, to file an amended income tax return.

2. Use Form 1040X to correct previously filed Forms 1040, 1040A or 1040EZ. An amended return cannot be e-filed; you must file it by paper.

3. Generally, you do not need to file an amended return to correct math errors. The IRS will automatically make that correction. Also, do not file an amended return because you forgot to attach tax forms such as W-2s or schedules. The IRS normally will send a request asking for those.

4. Be sure to enter the year of the return you are amending at the top of Form 1040X. Generally, you must file Form 1040X within three years from the date you filed your original return or within two years from the date you paid the tax, whichever is later.

5. If you are amending more than one tax return, prepare a 1040X for each return and mail them in separate envelopes to the appropriate IRS campus. The 1040X instructions list the addresses for the campuses.

6. If the changes involve another schedule or form, you must attach that schedule or form to the amended return.

7. If you are filing to claim an additional refund, wait until you have received your original refund before filing Form 1040X. You may cash that check while waiting for any additional refund.

8. If you owe additional 2011 tax, file Form 1040X and pay the tax before the due date to limit interest and penalty charges that could accrue on your account. Interest is charged on any tax not paid by the due date of the original return, without regard to extensions.
Links:

• Form 1040X, Amended U.S. Individual Income Tax Return (PDF 110K)
• Form 1040X Instructions (PDF 45K)
• Tax Topic 308 — Amended Returns

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