To file prior year returns with TurboTax, you would need the Desktop software for each prior year needed. Prior year returns cannot be e-filed. You can go to the following website for prior year TurboTax software (2015 thru 2017). Do not mail all the returns in one envelope, mail each years return separately.
Your 2018 return can be done Online or with the Desktop software:
What are the advantages of the TurboTax CD/Download software over the Online version? for your 2018 return.
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