The taxable amount not determined box is checked on my 1099-R from Charles Schwab. For instance say I had $10,000 in an IRA at the beginning of 2020 then contributed $6,000 of post-tax money to the IRA in May. Then in June converted the entire $16,000 (assuming no gains) to a Roth IRA at Charles Schwab. Shouldn't the taxable amount be $10,000 rather than the full $16,000? I am worried I am going to get taxed twice. Should I show the $16,000, from the 1099-R, as taxable then show a $6,000 non-deductible contribution for 2020? Or contact Schwab?
Thanks,