How do I amend a submitted filing done on 2/12/2021 because I received a 1099B on 2/19/2021 (after filing)?

[fanfare]

The AMEND function will be available later when TurboTax releases Form 1040-X.

That would be sometime in March.

[JohnB5677]

If you have already filled your taxes the first step is to wait and see if it is Accepted or Rejected. 

• If it is Rejected you will be able to correct the rejection error and add your anything you want..
• If it is Accepted you will have to wait and file an amended tax return:
  • If you're getting a refund wait until the refund comes in.
  • If you owe money wait at least two weeks before filing the amended return.  (This is so that the IRS has time to process the original return.)

To amend a return 

Some quick ground rules:

1. Be sure the original return was filed and accepted.
2. DO NOT go back into the return or change anything before you start the amendment process.
3. Gather everything you need before you start.
4. Complete the entire amendment process before you log out.
5. Starting with 2020 tax returns you can E-File a 1040-X amended tax return.  All prior years must be printed and mailed.

 You can correct a return that you've already filed and had accepted.  Select the year that applies and use this guide to proceed.

Select your tax year for amending instructions:

• 2020
• 2019
• 2018
• 2017

For additional information please refer to  How to Amend

The 1040X (Amended Return) tax form is scheduled to be available 03/25/2021.