When are you being asked to pay for TurboTax?
If you used and paid for one of the 2018 TurboTax online editions of either Plus, Deluxe, Premier or Self-Employed then you have access to all of your prior year online return up through October 2020. Provided you created the 2018 online account using the exact same User ID that was used to create the prior year online accounts.
To access your current or prior year tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
See this TurboTax support FAQ for accessing prior year online tax returns - https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/270...
