TurboTax send me the email below. I prepared the amendment but it said the efile was closed in Oct. Is efile allowed due to this bug?
"Because of an error in a TurboTax calculation, you have reported the cost basis of your Employee Stock Purchase Plan sales incorrectly, resulting in a possible overpayment of your federal tax and, if applicable, your state tax.
We fixed the issue in TurboTax, and we want to make sure your federal and state tax returns are complete and accurate. We recommend that you check and, if necessary, amend your tax returns to determine if any additional refund is due. There are no additional fees for checking your TurboTax return or for preparing an amendment."
No, you won't be able to electronically file your 2020 amended income tax return. You'll need to print and mail it in.
[Edited 1-23-2022|7:54 am PST]
For this issue, what forms do I need to mail in besides 1040X? For state, the instruction is to mail attach a federal return. Do I attach 1040 or 1040X?
For the federal return, you only have to send in the 1040X, unless the change involved needing to add another schedule or form. In that case, you would include the added form.
Not every state has the same set of rules. However, if the federal amend doesn't affect your state refund or liability, you would not send anything in. If it does, you would send in the state forms (dependent on the state) along with the 1040X.
Here is a little background on filing an amended tax return. IRS Guidance on an Amended Return