Before filing, be sure to make a copy for your records. Then, pay close attention to the instructions for submitting a 1040X so the IRS can process your amended return quickly. The IRS requires you to include any applicable forms or schedules (i.e., any and only the ones that support the change you are making) and asks you to put them behind the 1040X in the proper order.
To determine the order, look at the upper right corner of the supporting form where it says "Attachment Sequence No." and place them in order from lowest to highest. However, the IRS stipulates several forms that should be attached the front of the 1040X, including a W-2, 1099-R or 1042S. Check the instructions under "Assembling Your Return" for your specific case.
If you owe money, the IRS instructions direct you to include the check or money order (not cash) in the envelope. Alternatively, you can pay electronically at the IRS website. The IRS instructions state the amount should be for the original amount you owed — don't attempt to calculate the interest or penalties, but rather wait for a bill from the IRS. If you can't afford the amount you owe to the IRS, you can apply online at IRS.gov for monthly installments.
The IRS asks that you not attach the check with a staple or paperclip, but rather that you put it loose in the envelope and that you make the check out to "United States Treasury." The IRS instructions also direct that the check includes not only your name and address, but also your daytime phone number and Social Security number. (If filing jointly, include only the Social Security number that is listed first on the form). In addition, write the tax year you are amending.
If nothing else, perhaps this experience of examining the 1040X will help you better understand the income tax process, which you can explore further with the links on the next page.