Intuit is not using a true one logon; its an integrated session cookie across platforms. The accounts themselves are not truly integrated across platforms. I tried to logon to the help center here today, using the same logon that I created this post from yesterday, and it wouldn't work (in fact, I didn't even receive a notification that a response was posted to my inquiry from yesterday - I stumbled across it). Ran through the change password process - while using my same user ID, updated the password to what I used to logon yesterday through Mint portal; and once logged on here to the intuit forum, had to again, select a new username to use in this portal (hence jmbw1 today). It didn't even recognize the one I created yesterday for my same User ID, but through the session I had opened via Mint. I'm logged on now in Turbo Tax - but Intuit really needs to clarify the one logon experience; the accounts truly are still platform-independent.
