Turbotax W-4 Withholding Calculator is for tax year 2018. https://turbotax.intuit.com/tax-tools/calculators/w4/
"Can I find out what impact tax reform has on next year’s (2018) taxes?
Yes. You can estimate your 2018 taxes at any time with TaxCaster. It’s up-to-date with the latest tax laws and can calculate both your current, and future year taxes."
Both TurboTax Online and CD/Download versions are regularly updated; as is TaxCaster.
