How do I open a .tax2024 file on the online turbotax version?

You would need to download and install 2024 TurboTax on a Windows or MAC computer.  If you paid for online TurboTax customer service would be able to push a copy of the desktop version to you.

You can't transfer a 2024 tax file.   You need a 2023 tax file to start a 2024 return in TurboTax Online.   See - How to Switch to TurboTax Online

I want to view what Turbo Tax Online sent me when I filed my 2024 taxes.  Specifically the amount of my estimated quarterly taxes for 2025.

To access your tax return after you've e-filed it or printed it as part of mailing your return to the IRS, in TurboTax Online:

1. Sign in to TurboTax.
2. Select Tax Home from the menu.
3. Scroll down to Your tax returns & documents.
4. Select 2024, and then select Add a State (you're not actually adding a state, this just gets you back in).
5. You will now be in your return. Select Other Tax Situations on the left menu to find Estimated Taxes.
6. Or, to print a copy, go to Tax Tools on the left menu, then Print Center. 

See this help article for more information.

@jprochas 

@jprochas