IRA Contributions in 2020 for 2019

[jd114]

Under IRA contributions:

When I add contributions in the "2019" box, my tax due goes down.  When I add more contributions in the "2020" their is no change even though I'm allowed to add more for 2019 in 2020.  I know we have until July 2020 to contribute. Why is their no change when added to the "2020" box?  Can't I just add all in the 2019 option to get the reduce tax owed?  Thats what I've been able to do in the past.  

[Bsch4477]

You are completing your 2019 tax return so your 2019  IRA contribution, even though made in 2020, affects only your 2019 return. Any contribution to your IRA for the 2020 tax year will be reported when you do your 2020 return next year and should not be reported on your 2019 return.