The section of TurboTax where you indicate that you want to apply your state refund to next year is the "Estimated Payments section".
Follow the directions below to apply your 2018 state return to your 2018 state taxes:
- During the final review stage of your state return, you’ll reach a screen titled “A few things before we wrap you your state taxes”.
- Scroll down to other tax forms and click start/revisit across from "Make Estimated Payments for Next Year".
- Select Yes to start the state estimated taxes section now.
- On the next few screens as appropriate, you will determine what amount of your refund you want to apply to 2018.
- Completing the estimated payment voucher process will enable you to apply your refund to the estimates.
Please comment below if these steps do not work for you so I can assist you further.