@jdfrosch - the up-to $300 gets put into line 10b (I think - I'm at work and going from memory) of the 1040 worksheet. I don't remember if it gets put there automatically or not, but that's where it goes. It's a line that says it's your deduction if you use the Standard deduction. IMO that's not where that line should be because it's before you choose a deduction method, but nobody asked me.
But if you're asking about where the app includes the $300 difference when figuring out how to choose your deduction, the answer is "in the code." It doesn't show this number or explain it - it appears to just add it and base the outcome on it. All I can tell you is if you're having the problem I described at the top of my long post, just make a copy of your return file and run through the process in my post to test the different steps. It's complicated and my explanation is my best interpretation of what's going on and how to work around it. I literally cannot explain it all - that's why I wrote the post as a step-by-step process so people having this issue will see how it overrides your choice and how to fix it. You can also do a test where you add in enough to your itemized deductions to be well over (more than 300) the standard deduction and it in my case everything worked perfectly. That's why I'm zeroed in on that $300 difference and why it's only a small number of people having the problem. If you are having this issue, you can always "remember" $300 in cash donations and add them to your Schedule A, and this problem should go away.
BTW if you use my method to force the use of Itemized, make sure to go back to the 1040 worksheet and delete any entry in line 10b (and no, it won't accept zero - you have to delete it ffs). I think the "let's check for errors" page will take you to this if you don't remove it anyway.
