TurboTax retains online tax returns for the past seven years, the same retention period as the IRS.
Tax returns prior to to tax year 2018 are no longer available.
SAVE YOUR TAX RETURNS !
EVERY year before mid-October you should save a copy of your tax return as a pdf and print a copy of it for your records. That way you will not be searching online frantically when you need it for a lender, FAFSA forms, your next tax return, etc.
In order to transfer a past year return to the new return you need the tax file
NOTE: TurboTax and the IRS save returns for seven years. Returns older than seven years are purged.