When Box 2b on Form 1099R ("Taxable amount not determined") is marked by "X", how does the taxpayer make adjustment on NJ Form 1040 (Line 20B) so cost basis is not taxed?

[tiger72pu]

IRA Custodian does not know taxpayer's cost basis from prior year's rollover so he cannot determine taxable portion of RMD. But from IRA Information Worksheet from prior year's Form 1040 (prepared by TurboTax), tax basis info is known to taxpayer. Can this revised value somehow be entered into TurboTax software to override Form 1099R's data feed (which is showing (incorrectly) that 100% of withdrawal is fully taxable)? If so, what steps must be followed? Will this change be programmed into next TurboTax revision of NJ 1040 form?

[fanfare]

TUrboTax NJ supports your situation : it will ask you about it in the Q&A portion.

[tiger72pu]

Fanfare: I see no such Q&A from TT - NJ ....  Where would I find their response/interrogatory? ... on this webpage, within the app? or somewhere else? 

[tiger72pu]

I finally figured it out once I decided to reply to the NJ State inquiry if one of my two IRA accounts experienced its INITIAL withdrawal in CY2024. Once I answered in the affirmative & then, when prompted, reinputted the IRA Contribution Worksheet info from the federal side into the NJ State side, the math worked as I had earlier calculated (from doing it long hand with NJ's Form 1040 Instruction Manual). Hopefully, this issue will not reoccur in future tax years using TT Online. Thank you.