Is any of my data stored on-line, if I use the online TT facility, and if so, what options are there for deleting the online data between sessions?

If you use TurboTax Online, then your tax returns are stored on our secure servers. Unfiled returns can be deleted at any time, but deleting them means you won't be able to edit or view them the next time you login. Returns that you have submitted via NETFILE can only be deleted if you delete your account.

Editable copies of returns (filed & unfiled) are available for 3 years, while PDF copies of Filed returns are stored for up to 7 years.