@DawnC ... okay, I did some more investigation, and I believe this is definitely some sort of bug in TurboTax's online interface at least, and possibly also in the calculations.
Here's my findings:
1) I initially thought maybe it's some issue with my TurboTax data for 2024 tax filing. Since I had already paid, I couldn't 'start over'. I then created a new Intuit account and created a new 2024 tax return from scratch via this new account. Even in this new account, the symptoms I mentioned above were the same: the tax due number suddenly increases after crossing 'Federal Review' screen with me doing no additional change. While doing this, I was also on the phone with TurboTax support for 1.5 hours to try and see if she can help. But since both account's behavior was the same, the agent in the end told me it's likely that the $4924 calculation is correct as it's a double confirmation that the amount is the same, and I should be okay filing my return. So I filed my return earlier today, hoping this is behind me.
But now based on your suggestion, I used the second account's tax filing process to do more digging.
2) As I said earlier, the tax due number increases when the screen transitions from Federal Review to State taxes pages, and this is happening in the second account too. During this page transition, the tax due number increases. If however, I avoid going to State taxes and directly jump to 'Review' section (using the bookmarks on the left of the screen), the tax due number does NOT change !!!, i.e. it remains at $4093 tax due for me.
3) I finalized my return in the second account too, and then compared the PDFs as you suggested, both with the $4093 (by directly jumping to 'Review') and $4924 (by going from 'Federal Review' to state taxes) tax due versions. Turns out both PDFs are exactly the same. They both mention the higher $4924 tax due amount. This is true even for the case when I jump directly to 'Review' screen and the tax due amount on the screen shows $4093 for me. So this is a mismatch between what the screen is telling me, and what the PDF is telling me, which means it's a bug somewhere.
Since I've already filed my tax return based on the agent's suggestion, I'm now unsure which total is correct and which is incorrect.
