To treat this as 2021 income you would enter the substitute 2021 Form 1099-R (Form 4852) into the 1099-R section of 2021 TurboTax by marking the checkbox that tells TurboTax that you are entering a substitute Form 1099-R. The TurboTax will include on Form 1040 as taxable income the amount amount you enter in box 2a. TurboTax will also prompt you to enter the explanation to be included on the Form 4852.
Since the brokerage will be issuing a 2022 Form 1099-R reporting this income, you'll also need to include a substitute 2022 Form 1099-R with your 2022 tax return to show that this distribution was not received in 2022.
