You do not say when you filed it. Did you e-file it timely in 2020? Or did you file late by mail?
If you e-filed it and it was rejected without you realizing it, then you can only print sign and mail it now. Or if you mailed it sometime within the past year, it might still be in a pile of unopened mail waiting to be processed.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.
If you owed tax due your only proof that you paid is your own bank or credit card record. If you are getting a refund there is no penalty for filing late.
If the IRS sent a request for a signed copy of the 2019 return for what ever reason then comply with the request. If you owed on the return and you paid the balance due then also send a copy of the email acceptance or the history report showing the return was filed timely.
I e-filed it and got an email that it was accepted. Now they say they never got it. My return is trapped in a backup drive I can't open. What do I do?
Did you have a tax due? If your return was Accepted maybe they didn't get your tax due payment. Or Contact Customer Service
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https://support.turbotax.intuit.com/contact/
What is the Turbo Tax phone number
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632