After you file

You can do this a couple different ways. When you are doing the amend and have finished making changes, click Done at the bottom of the screen that asks What do you need to change on your return? and continue through until you reach the Why did you need to amend your return? screen and you can type your explanation there and Continue

Or, since you have to print and mail the amended return, you will handwrite an explanation in Part III—Explanation of Changes of the 1040X on the second page. And if you need more space to write, you can attach an additional handwritten statement. You'll find details on that here Instructions for Form 1040X on page 14 as well. 

Amended returns have to be printed and mailed. They can't be e-filed per IRS regulation. It is recommended to wait until the IRS has accepted your initial return and you have received your federal refund before you amend the return. If you've closed out of your amended return, use steps below to print a copy to mail. We highly recommend you save a copy for your own records in case you need it again in the future.

NOTE: The amend instructions for 2017 can be found here if needed How do I amend a 2017 return in TurboTax?

Detailed Instructions if using TurboTax Online

  • Log into your account and click Tax Home
  • Scroll down to Your Tax Returns and Documents and click Show More
  • Highlight the year of the return you amended
  • Click on Add a state (not adding one, just a way to get in and print)
  • Then click Tax Tools to the left and Print Center
  • Select Print save or preview this year’s return
  • Check the box next to returns you want and choose forms to print
  • Then click View or print the forms
  • Mail to the address specified in your return.

Detailed Instructions if using TurboTax CD/Download software

  • Open your amended return.
  • Click on File and then Print.
  • Mail to the address specified in your return.

Once you mail an amended return, it can take up to 3 weeks before it shows up in the IRS's system. So give it that amount of time before you start checking for any updates on it. After 3 weeks, you can go here Where’s My Amended Return? to check the status of it. 

Amended returns can take up to 16 weeks to be processed once they receive it. And you can find a list of frequently asked questions, about amended returns, here Form 1040X, Amended U.S. Individual Income Tax Return, Frequently Asked Questions