You need the 2024 return file ending in .tax2024 to Transfer into 2025. You can not upload or import a 2023 return to Online now. How did you do the 2024 return? Online is only for 2025 now . You can transfer 2023 into a new 2024 tax return on your computer. But you need to use the 2024 Desktop program. Then if you get the .tax2024 file you can transfer it into 2025 online.
To do a 2024 tax return you have to buy the Desktop program here,
https://turbotax.intuit.com/personal-taxes/past-years-products
You will need Windows 10 or Mac Ventura 13 to install it on.
