Deductions & credits

The "math" requires knowing the *2019* total year end value of ALL Traditional, SEP and SIMPLE IRA accounts in order to prorate it. The 2018 value in immaterial.

If there is after-tax money in the IRA then ALL distributions (including Roth conversions) will include some after-tax money.   That calculation in done on lines 6-15 on a 8606 form.

Since you did not file a prior 8606 form the enter the known amount of after-tax when the interview asks for it.  If it asks for an explanation - just say it is after-tax money from a 401(K) rollover.

Enter a 1099-R here:

Federal Taxes,
Wages & Income
(I'll choose what I work on - if that screen comes up)
Retirement Plans & Social Security,
IRA, 401(k), Pension Plan Withdrawals (1099-R).

OR Use the "Tools" menu (if online version left side) and then "Search Topics" for "1099-R" which will take you to the same place.

Be sure to choose which spouse the 1099-R is for if this is a joint tax return.
Be sure to pick the correct 1099-R type: Standard 1099-R, CSA-1099-R, CSF-1099-R, RRB-1099-R.

[NOTE: When you get to the "Your 1099-R Entries" screen where you can add another 1099-R, use "continue" to keep going as there are additional interview questions after that screen in most cases. You can always return as shown above.]

You will be asked of you had and tracked non-deductible contributions - say yes. The enter the amount from the last filed 8606 form line 14 if it did not transfer. Then enter the total value of any Traditional, SEP and SIMPLE IRA accounts that existed on December 31, 2019.

That will produce a new 8606 form with the taxable amount calculated on lines 6-15 and the remaining carry-forward basis on line 14.

You can NEVER withdraw ONLY the nondeductible part - it must be prorated over the entire value of ALL Traditional IRA accounts which include SEP and SIMPLE IRA's. (For tax purposes you only have ONE Traditional IRA which can be split between as many different accounts as you want, but for tax purposes they are all added together).

For example using rough figures: if you had $60K of nondeductible contributions in an IRA with a total value of $600K (10:1 ratio), then when you take a $60K distribution from any IRA account $6,000 would be nontaxable and $54,000 would be taxable (same 10:1 ratio) , with the remaining $54K of basis staying in the IRA for future distributions. As long as there is any money in the IRA, there will be some basis.

TurboTax will ask for your non-deductible "basis" and then the *Total Value* of *all* Traditional IRA, SEP and SIMPLE accounts as of Dec 31, of the tax year. That is so the prorating of the basis can be properly proportioned between the current years distribution and the remaining IRA value. That is done on the 8606 form.