If you file your federal tax return with the wrong Social Security number, the Internal Revenue Service may not be able to match it to your previous records. This can saddle you with costly penalties and interest for years of unpaid taxes that aren't even your fault. The IRS allows you to file Form 1040X to correct existing tax returns for three years after the date you filed the original return or two years after the date you paid the tax, whichever is later. The form is the same for all tax years you will be amending, but you must file a separate form for each year.
Download Form 1040X from the IRS website. Enter your correct contact information in the top section of the form. List the correct Social Security number here. You will have an opportunity to explain the correction in a later section.
Check the appropriate box to indicate your filing status, such as "Single" or "Married Filing Jointly." You must check a box even if you are not changing your status from the previously filed return.
Copy the income items, deductions, tax liability, payments and refunds from your original tax return to the corresponding lines of Column A of your Form 1040X if you are revising any of these amounts along with correcting your Social Security number. Enter the net change of each item in Column B and the corrected amount in Column C. Skip this section if you are not making any changes to the previously reported amounts.
Complete Part I of the form if you are changing the number of exemptions for you or your dependents. If you did not include a $3 donation to the Presidential Election Fund on your original return but would like to add one now, check the box in Part II. This donation will not increase the amount of tax you owe.
Explain your changes in Part III of Form 1040X. If you are also changing any previously reported dollar amounts, attach any pertinent W-2s, 1099s or other supporting schedules corresponding to the amended totals.
Sign and date the bottom of the form. Make a copy for your records and mail the original to your local IRS office. Consult the instructions for Form 1040X to find the appropriate mailing address for your area.
Denise Sullivan has been writing professionally for more than five years after a long career in business. She has been published on Yahoo! Voices and other publications. Her areas of expertise are business, law, gaming, home renovations, gardening, sports and exercise.