Why do I get an error when I entered the date of my spouse who past away in Aug 2020, it says Cannot be before 01/01/2020

It sounds like you may have entered the date incorrectly.

You will need to review the entry in the My Info section of the program though to reflect the date of passing for your spouse.

1. Log back into TurboTax
2. Select the black panel on the left hand side of the screen and select My Info
3. Under the page titled Personal info summary, scroll down to the information for your spouse and select Edit to the right of your spouse's name
4. Scroll down to section 3, A few other things we need to know.  You will be able to answer the questions here.  
5. Carefully review your input for the date your spouse passed away to ensure the format is entered as reflected in the sample below.

I am sorry for your loss.

Turbotax will sometimes auto-complete dates in a weird way.  Try writing out "08/15/2020" rather than abbreviating.