I have a .tax2015 file from last year's tax return I did on TurboTax software. Is there a way to upload that to my online account so I could view it online?

There is no way to upload your .tax data files to TurboTax Online and store them there. There is no way to view them online. The only way to view them is with the software for the year that you want to view.

You should save your tax returns as PDFs as well as saving the .tax data files, so you can easily view them in Adobe Reader. And make backups of your .tax and PDF files on a removable storage device such as a flash drive, external hard drive, or CD, or in cloud storage. TurboTax does not have copies of them. If the hard drive on your computer fails, you will lose all your tax returns if you do not have backup copies.

Thank you for a very clear (non-generic) reply!  I can't believe that such a big company like TurboTax would not have the ability to store your tax information to your TurboTax account especially since it seems like people that do their taxes through TurboTax Online can do that (or is that not the case?).  I also can't believe that the latest software version cannot open previous years taxes, requiring us to save the installation file of TurboTax of previous years.  These seem like basic fundamental functions such an advanced software should have.  No backwards compatibility? Seriously?  Maybe TurboTax is not a very good long term tax solution after all.

No tax software has backward compatibility, not even professional software. It would be too hard to implement because of the large number of changes in forms and rules from one year to the next.

Oh it's do-able they just don't want to mess with it and like you said seems like not making it backwards compatible is this industry's standard.  Thank you for your replies.