You have to wait until the IRS either rejects or accepts your return. If your return is rejected, you will be able to go into your account and add or change it and resend it.
If the IRS accepts your return, then you have to wait until it has been fully processed and you have received your refund. THEN you can prepare an amended tax return 1040X and mail it in. You cannot e-file an amended return. Meanwhile, DO NOT change anything on your return until you start the amended return. If you did change or add the missing info then take it out and put your return back to the way it was when you first filed it.
How to amend an Online return
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Yes, you are correct. If you filed with some other company other than TurboTax, it is best to go back to them to have them amend it. It is easier than trying to recreate your original return in TurboTax. If I am wrong and you did file with Turbotax, you will wait until your return is accepted and then you can amend. Here are the instructions:
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