If there is any amount in box 5 (the nontaxable portion of this distribution) of this Form 1099-R, the taxable amount is less than $12,000 because the repayment is applied first to the taxable portion. Examine Form 1040 line 5b to see how much is being included in income.
Assuming that there is nothing in box 5 of the Form 1099-R, depending on your other income and your filing status, your income tax liability might be zero no matter if the $12,000 is applied entirely to 2020 or as $4,000 in each of 2020, 2021 and 2022. Examine Form 1040 line 22 to see your income tax liability each way.
If you have no tax liability with the entire $12,000 applies to 2020, it wouldn't make sense to spread it out over three years.
