Questions about Wrong Total basis in Traditional IRA on form 8606 from previous year

[wife-mom-math]

Hi,

In year 2021, my 8606 Total Basis is $6,000.

In year 2022 and 2023, my Traditional IRA contribution were tax deductible (so no 8606 produced).

In year 2024, my Traditional IRA contribution is $7,000, but the 8606 Total Basis is $0 (it should be $6,000, from year 2021, somehow Turbotax didn't carryover the Total Basis from 2021). -- I didn't realize this mistake.

So two questions:

1) How should I correct the wrong Total Basis in 2024?

2) I am about to file my 2025 tax, should I put in the corrected Total Basis, i.e., $6,000 (from 2021) + $7,000 (from 2024) = $13,000 Total Basis?

Thank you for reading.

[baldietax]

1) you'll need to send in the updated 8606 for 2024 to record the cost basis, in similar threads it's advised to send a 1040X with it, see

https://ttlc.intuit.com/community/retirement/discussion/amend-tax-return-for-form-8606/00/3301099

https://ttlc.intuit.com/community/after-you-file/discussion/amend-form-8606/01/3428188#M767296

see also end here for prior year basis updates (tho this refers to missed 8606 filing altogether and states "Don’t amend your 2024 return to record your basis")

https://ttlc.intuit.com/turbotax-support/en-us/help-article/retirement-benefits/enter-backdoor-roth-...

2) yes update the cost basis in the interview question to reflect the correct carryover from 2024, which will go onto Form 8606 Line 2.

https://www.irs.gov/pub/irs-pdf/i8606.pdf

@dmertz @VolvoGirl @Mike9241 @DoninGA @mesquitebean 

[wife-mom-math]

Thanks for your reply!

I tried to submit the 2024 amend via Turbotax. However, Turbotax seemed to require submission of Illinois 1040-X as well, although there is no change in tax liability. I only made 1 change in the total basis of 2024 8606 Federal. 

Is submission of Illinois 1040-X necessary? (for a total basis change in Federal 8606)

[DianeW777]

Some states do require an amendment if there is a federal amendment, I would just go ahead and file both even though there is no change to the Illinois (IL) as well.

@wife-mom-math 

[wife-mom-math]

Hi @DianeW777 , thanks for your reply. Do I need to submit just IL-1040-X (and the changed doc, in this case Fed 8606), or do I need to resubmit the whole stack IL-1040 and the rest as well?

[DianeW777]

Submit only the changed Form 8606 and the amendment page IL1040-X. It should be sufficient since nothing else has changed so both amendments (federal and state) would be the same..

@wife-mom-math 

[wife-mom-math]

Thank you for your fast reply!! @DianeW777