I read you can contribute to your 2019 IRA up until July 15 2020. But Turbo Tax has an option for 2020 contributions. It doesn't seem to benefit me if I increase that contribution. Meaning no decrease in tax owed. However, any addition under 2019 IRA contributions does decrease my "tax owed." Can I just add all my contributions from 2019 and 2020 under the 2019 contribution option?
Yes, if all contributions were marked for your 2019 IRA. The question is not about what year you make the contributions. The question is asking, when you went to your broker, which box did they mark that the contribution is being made for.
You can only contribute so much per year. The point is to make sure you are not putting in too much to your 2019 account.
If you tell your broker to mark all of your contributions for the year 2019, that is what you put in the program. If you have not made full contributions to your 2019 account, it is best to put up to $6,000 there ($7,000 over age 50) first before going to 2020 contributions.
You can only deduct 2020 contributions that are marked for a 2019 contribution by July 15.
Related:
Who can contribute to a Traditional IRA?
Can I contribute to both a 401(k) and an IRA?
Can I contribute to both a traditional and a Roth IRA?
By what date do I need to contribute to my IRA to get the deduction?
My AGI was reduced when I entered an amount in the Step-by-Step box on the screen "Tell us How Much You Contributed" in TurboTax Home and Business 2019. However, since I made the contribution after 1/1/20 I entered that amount in the second box, and the AGI reduction went away. Does it have something to do with having withdrawn that amount in excess of the minimum during 2019? Or is it because I turned 70.5 on 1/16/2020? My tax advisor can't figure it out either, and I've been unsuccessful mining IRS publications. What is going on in TurboTax?