Deductions & credits

Thank you for your response, it's very comprehensive. There is one part I don't understand. The calculation of my 2019 RMD was based on my IRA balance at 12/31/18. I'm now preparing my 2019 taxed and have to pay tax on the RMD some of which is after-tax dollars. Why does the math require my 2019 ending balance? That impacts my 2020 RMD. 

 

My question is the same for the Roth rollover, I need to pay the 2019 tax on the rollover some of the amount includes after-tax dollars. Again, why does the math require my 2019 ending balance? I have to pay tax on the rollover amount in 2019?

 

Thank you