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:
If you have more questions about this, ask in the comment box below.
https://ttlc.intuit.com/replies/3288565
