It's really unusual to have taxes withheld from a return of contribution, particularly on a code JP Form 1099-R. In this case, you would need to report the 2017 Form 1099-R on both your 2016 and 2017 tax returns. TurboTax knows that the amount in box 2a is income (potentially subject to penalty) on your 2016 tax return but that the tax withholding is reportable and creditable on your 2017 tax return.
