I have been entering my earnings and other details on my Turbotax desktop software. When I update the software, does the updates apply to the data already entered previously in my tax forms?
When you update your software in TurboTax Desktop, it does not affect the data you have entered. If the update changes a calculation that uses that data or updates where that data flows, then the program will use your existing data in the new calculation or data flow. In other words, updating your software after you've already starting entering data won't have any negative affects on your information. You won't lose any of the data you have entered.
The update does apply to all the data.
Therefor, your refund/tax due may change as soon as you update.
How about Software updates that arrive, and I have already filed my returns, and they have been accepted and processed.
Make sure you saved your return as a pdf file after you file and before you do any new future updates. Then you can compare your return with the updates to your filed return. I would save your filed return pdf with another name so it doesn't get overwritten like add FINAL to the name.
In Windows you can change the auto update setting for it to ask you before updating. I always change the settings right after I install the program. Go up to Online-Updater Preferences and select Ask me before getting updates.