I believe you are right about the Mac and that there is no way to prevent TT from auto updating the app each time it is opened. The more I think about it the more sense it makes to never turn off the auto update feature since in the end the best version of the software will be the most updated version -- i.e. it will produce the most accurate version of any tax return. So let it update every time the app is launched. The best solution to maintaining a copy of a tax return that is identical to the one filed with the IRS is to save a copy of the return as a .pdf which can never be changed by future auto-updated versions of TT. If the IRS questions the tax return, say six months after filing, you will have the .pdf which is identical to the return that was filed and you will also have a .tax version updated with the most recently auto updated TT app. And remember, over that six month period the software used by the IRS has probably changed too, which obviates the idea that turning off the auto update feature would have ever helped in the first place.
So in the end, keeping a .pdf copy and also allowing TT to auto update is probably the best solution.
