Your basis in nondeductible traditional IRA contributions is the amount shown on line 14 of your 2021 Form 8606 plus any nondeductible traditional IRA contributions you have made for 2022.
Because the rollover to the 401(k) is only permitted to consist of pre-tax money, your basis is left in the the traditional IRA to be applied to the Roth conversion. With a zero balance in traditional IRAs at the end of 2022, all of your basis will be applied to the Roth conversion. If the amount Roth conversion equals the amount of basis as determined above, the entire Roth conversion will be nontaxable.
To be done in 2022, the distributions from the traditional IRA must be completed by the end of 2022. The timing is mainly based on the ability of the traditional IRA custodian to process the distributions from the traditional IRA, but also on the willingness of the 401(k) plan to accept the rollover of the pre-tax portion.
