Nondeductible traditional IRA contributions are those for what you did not take a deduction and instead reported in box 1 of Form 8606, or came to be in the traditional IRA from rolling over after-tax funds from an employer's qualified retirement plan like a 401(k) (which would be includible on line 2 of Form 8606 the next time Form 8606 Part I is required to be filed for some other reason. Lines 1 and 2 of Form 8606 are summed on line 3, are applied proratedly to traditional IRA distributions. Basis that remains appears on line 14 to carry forward to line 2 of the next Form 8606 that you file.
If your originally filed 2022 8606 failed to include on line 2 the amount from line 14 of your previously filed Form 8606 (2021 in this case), yes you should ament to correct the 2022 Form 8606. Failing to prepare the Form 8606 correctly does not mean that the basis did not apply to the Roth conversion, it means that you lose the credit for that basis and your basis is still reduced going forward. You are not permitted to selectively choose the years to which the basis applies.
