Backdoor Roth IRA Conversion 2020 and Excess Contribution

You should receive a 2020 1099-R with a code P of JP in box 7 depending if the return was from the Roth or Traditional IRA.   Only any earnings attributed to the excess would be taxable.  The taxable earnings should be reported by the IRA trustee in box 2a.  Just enter the 1099-R into TurboTax.

The "backdoor Roth" is totally separate.

The "Backdoor Roth" does not exist in tax law. It is a procedure used by some to take advantage of a quirk in tax law that allows making a non-deductible contribution to a Traditional IRA when one cannot contribute to a Roth IRA, and the immediately converting the Traditional IRA to a Roth IRA, thereby getting the money into the Roth via "backdoor".

That "procedure" can only work of all these requirements are met:
1) No Traditional IRA account whatsoever can exist (that includes any SEP or SIMPLE IRA accounts) at the start.
2) The Tradition IRA contributions must be reported on a 8606 form as non-deductible.
3) The conversion to a ROTH must be shortly after the contribution to avoid taxable gains.
4) The entire Traditional IRA value must be zero that the end of the year of conversion.

Otherwise the conversion will be partly taxable.

First you must enter your Traditional IRA contributions (if there were 2019 contributions).

IRA contribution
Federal Taxes,
Deductions & Credits,
I’ll choose what I work on (if that screen comes up),,
Retirement & Investments,
Traditional & Roth IRA contribution.

Be SURE to answer the follow up that the are choosing to make this contribution NON-DEDUCTIBLE - if that screen comes up. (DO NOT say that you moved (recharacterized) the money to a Roth) – this is a conversion, not a recharactorazition.

Then enter the 1099-R that shows the distribution.

Federal Taxes,
Wages & Income
I’ll choose what I work on (if that screen comes up),,
Retirement Plans & Social Security,
IRA, 401(k), Pension Plan Withdrawals (1099-R).

Answer the follow-up questions answer the question that you moved the money to another retirement. The screen will open up with choices of where it was moved. Choose you converted it to Roth IRA.

When asked if you have made any non-deductible contributions say " "yes" if you did then enter the non-deductible contributions made for tax years before 2019.     (Usually zero unless you also made a 2018 or earlier non-deductible contribution. If you do have prior year basis then enter the last filed 8606 line 14 value.).

Enter the 2019 year end value of your Traditional IRA a "0" (zero) - if it is in fact zero - this tax free Roth conversion will not work if it is not zero.

[If you had any other Traditional IRA at the end of 2019, then the nondeductible "basis" must be pro-rated over the current distribution and the total IRA value and only a portion of the Roth conversion will be non taxable and part will be taxable, with the remaining non-deductible basis carrying forward for future distributions. You can never only withdrew the nondeductible basis as long as the IRA exists and has a value more than zero.]

The non-deductible amount of your contribution will be subtracted from the taxable amount of the conversion on then 8606 form and enter on line 4a of them 1040 form and a zero taxable amount on line 4b if you did it right.

Also see this TurboTax FAQ:
https://ttlc.intuit.com/questions/4350747-how-do-i-enter-a-backdoor-roth-ira-conversion

Will I need to fill out a 5239 form for the excess contribution?

Since the return of contribution occurred in the same year as the contribution, 2020, the Form 1099-R will have codes J and 8, not J and P.  Any gains required to be distributed with the returned $2,000 will be subject to tax and to a 10% early-distribution penalty on your 2020 tax return.  As macuser_22 indicated, 2020 TurboTax will handle this when you enter the Form 1099-R that you will receive near the end of January 2021.