Yes, TurboTax is correct. You are a "cash basis" tax payer. It doesn't matter what year the state income taxes are for, what matters is when you paid them. You paid them in 2018 so they are reported on the 2018 income tax return and subject to 2018 tax law.
Most individuals are
cash basis, calendar year taxpayers. Under the cash method, income is
not counted until cash (or a check) is actually received, and expenses
are not counted until they are actually paid.
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