Correcting Non-Deductible Traditional IRA basis in form 8606

[TaxRookie7]

Hi, 

Back in 2016, I somehow restarted from zero my basis from what I had before.  I did not realize this until now as I am doing my 2021 taxes.  I would like to correct it.  Can I just update my 2021 - 8606 form with a new basis number - basically adding in what was the basis back in 2015 to my current  total.   Or do I need to amend all the prior tax returns somehow.  Note none of these should impact my tax for each year since they were non-deductible. 

thanks for any help!

[DanaB27]

No, you cannot just change your 2021 Form 8606. You will have to correct the previous Forms 8606.

You can correct Form 8606 on standalone basis if the changes won't affect the rest of the return. Otherwise, you will have to amend your tax returns.  

Please see Form 8606 and Instructions.

[TaxRookie7]

@DanaB27  Thanks for the reply!

I have seen some other members that are not able to just do a standalone 8606 and that the IRS asks for a 1040X to go along with it, as a standalone 8606 can only be done if you don't need to file a 1040?

If I need to do a 1040X, it seems like the amendments can only be done 3 years after you file the return?  Or since there is no change to the taxes can I go back to 2016 and 2017 years and fix them too. 

thanks!