Hello. Thanks for your answer.
I'm not sure you understand my question, or what TurboTax is telling me. Let me explain step-by-step:
1. My Tax Due box has a big number in it. I'm now ready to work on the IRA deduction, so I go to that screen - "Tell Us How Much You Contributed". The screen asks for TRADITIONAL IRA contributions, and I enter $6500. When I click Continue and go to the next screen, I can see the Tax Due number dropping by over $1000.
2. I click the Back button and return to the screen in which I entered the $6500. I now enter the same number, $6500, into the box that asks what part of the above amount was contributed up until April 15, 2019. When I click Continue and go to the next screen, I can watch the Tax Due number going back up to its original, bigger number. This would seem to indicate that the program isn't recognizing that the contribution is valid towards my 2018 earning, which is counter to what the law allows.
Nothing I've said here or done indicated that I've had a "taxable amount of distributions that occurred in 2018", as your answer stated, so I believe that's irrelevant. The problem SEEMS to be that when I enter in a contribution, the program "gives me credit" for it, and when I say that the contribution occurred between Jan 1 and Apr 15, 2019, the program takes it away. This appears to be a problem with TurboTax.
Please note (again) that there is nothing on that screen that allows you to choose whether the contribution is for a Traditional or a Roth, which Daniel mentioned in his earlier answer. The screen ONLY deals with Traditional contributions.
[And just a side, but related, question: If the program knows from your W-2 info that you're covered in an employer's retirement plan, then why is the Tax Due box changing when you enter in an IRA contribution? The program should know and tell you that you're not eligible for an IRA deduction because you're covered by an employer's plan. Or am I misunderstanding something? But please don't concentrate on this part of my post; it's the earlier problem that really seems to be a TurboTax bug and is giving me 2 different Tax Due amounts over $1000 apart.]