I have contributed post tax money to a nondeductible IRA in 2019, 2020, 2021 of $6000 each year. Each year, I have completed a back-door roth IRA conversion that same year that I have contributed to my nondeductible IRA. My first year (2019) basis was zero. My question is, does my basis increase each year by $6000 or does my basis return back to zero once that back-door roth ira conversion was performed.
