Get your taxes done using TurboTax

Appreciate the advice in this thread, I am in a similar situation to the original author except with an added complication and would welcome any insights.  At the end of 2020 I had a balance in a Traditional IRA account and this generated an increase in taxes due.  I am considering all options and wanted to know how I can reverse the backdoor conversion to Roth and treat my contributions as non deductible IRA contributions for 2019 and 2020 (both made in 2020).  I understand I can do this without the 6% penalty for 2020 (if completed by 5/17/21).  For 2019, will the penalty be 6% or 12%?  If I choose to do this in TT, what are the steps? thanks