Get your taxes done using TurboTax

@JamesG1 

Thank you for your prompt reply and advice.  To be clear, I am using the downloaded Turbo Tax Premier on a Windows 10 PC.  The module name and version number are shown below:

My filing status is Married Filing Jointly.  Turbo Tax says that the standard deduction is best for me.  I made $5050 cash donations to charities last year, and I want my $600 CARES Act deduction :-).  As an exercise, I followed your directions and deleted the charitable deduction entry.  My return passed Smart Check and my Federal tax bill increased by $62, as expected.

Then I went back and reentered my charitable deduction, to see if I could repeat the problem I had experienced.  When I reviewed my federal return, Smart Check said all was well, per the screen shot below.  Note the Federal refund amount.

Next I went over to the final review phase.  Here's a screen shot at the point where analysis was complete and I'm about to review the results:

Here's the results window.  Note that the Federal refund number changed to $103:

When I hit the Continue button, I get to the problem I described in my first post:

Here is where it gets weird.  I go back to the Federal Review section, and run the Federal Review.  Here's what I see when I am about to start.  Note the Federal refund number:

Here's that I see when I hit the Continue button and Turbo Tax takes me to the next window.  The Federal refund number changes as I watch!  I can verify in my 1040 form that the CARES Act deduction number changed from $300 to $600.  (I have redacted my income numbers here.)

Now Turbo Tax is ready to check my Federal Return:

And I am back where I started:

I can repeat these steps at will, and get the same results every time.  The final check introduces an error, and the Federal check fixes it.  Every time. 

I strongly suggest that indicates a defect in the version of Turbo Tax that I am running.  Someone from the Intuit development team should investigate this defect.