These amounts get entered in the Federal return section of TurboTax.
Below are steps to be brought to the section of TurboTax where you can enter in your estimated tax payments.
When you get to the section for Estimated Taxes, before you select to START, scroll down to see where the option is for 2017 Refund Applied to 2018. See sample screenshot attached. Once you complete entering your estimated tax payments, go back to this screen to scroll down to enter the 2017 refund applied to 2018.
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