I think what you are saying is that you overpaid but also underpaid taxes in past years but it mostly evens out, so no sense in going back and correcting everything. Also, there was no attempt to defraud the government as you were unaware of the misreporting. If you got audited penalties would be assessed on your tax due but the correct thing to do would be to file amended returns. You can only amend a return for a refund going back three years from the due date of the return, so if you needed a refund for overpayment of tax in a year beyond that timeframe to offset a tax due from another year, it may not be available to you.
Also, Form 8606 Non-Deductible IRAs would need to reflect your correct cost basis. You can accomplish this through your answers to questions after your enter the 1099-R forms in the current year. It may also be helpful to use the desktop version of TurboTax as you can work directly on the forms in many instances.
[Edited 3/7/25 at 9:02 AM PST]
@michinori-kaneko
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