E-filing for 2021 has been closed since October of 2022. The only way to file a 2021 tax return now is by mail; however, it is too late to receive a refund for a 2021 return unless you had an extension for the return. What does it say in your online account?
What does the IRS letter say? Does the letter say that you owe tax due for 2021? If so, the only proof that you paid will be your own bank or credit card records.
You say that you got "confirmation" that you filed.
When you e-file your return you will get two emails from TurboTax. The first one will say your return has been transmitted; the second one will tell you the IRS has accepted or rejected your federal e-file. If you filed a state return, there will be a third email (usually a day or two later) that tells you if the state e-file was accepted or rejected.
What does it say in your account? Does it show that the return was accepted? Or does it say something else---like "rejected," "printed," or "ready to mail?”
If you discover or realize that your e-file was rejected, you will need to print it, sign and date it in ink, and file it by mail now, since e-filing is closed for returns for tax year 2021.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**