@Jaguar , if you had the Roth 401(k) excess contribution for 2021 returned in 2022 by April 15, there is nothing to report of it on your 2021 tax return but you'll report any attributable gains on your 2022 tax return by entering the 2022 Form 1099-R that reports this corrective distribution.
If you did not have the Roth 401(k) excess contribution distributed timely, the excess contribution and attributable gains are the first amounts distributed from the Roth 401(k) and are taxable regardless of when they are distributed, resulting in double taxation (because the excess contribution was made with after-tax funds).
