You can enter a code JP 2019 Form 1099-R into 2019 TurboTax, but if it shows no tax withholding 2019 TurboTax knows to ignore it other than to remind you that the transaction was reportable on your 2018 tax return.
Entering the code JP 2019 Form 1099-R into 2018 TurboTax and telling 2018 TurboTax that it's a 2019 Form 1099-R will cause TurboTax to properly treat the amount in box 2a as taxable and subject to an early distribution penalty. If the box 2a amount was not already handled this way on your 2018 tax return, you must amend your 2018 tax return to add this.
