Hi,
I have the 2019 TurboTax Deluxe on my laptop. If you are using the same product, you can still open the 2019 TT without disturbing your actual filed 2019 return. To estimate how much federal tax you need to withhold in 2020, open the federal tax tax in your 2019 TT; click on "other tax situations" at the top of the screen; when the next screen opens, click on "Form w-4 and estimated taxes" which is located at the bottom of the screen.
