I was reading answers for a person looking for in-home health care and they stated that their Father would not lock up his financial paperwork. I was thinking about getting in some help but now it looks like I might as well give up. I can't lock everything up!
In my Dad's case, we have filing cabinets that lock. These are located in a room behind a door that we also installed a key lock on. He has no interest in (or real understanding of) any of this paperwork anymore, so never needs to go in there, and I have secured his copy of the key in his house where it cannot easily be stumbled upon.
This being said, 2much2cover is right ... you can't control what comes in the mail, and this is especially problematic during "tax record" season when lots of sensitive info is arriving ... I'm still trying to work out a good solution to that problem. But in general, I really think it's wise to make the effort to figure out a way to lock up the sensitive stuff. And there are silver linings to doing it, too -- in the process, I discovered insurance policies and other accounts that I didn't know existed and that Dad had forgotten about, which made it easier for me to help his accountant file more accurate tax returns, etc. Also got rid of a ton of stuff that we didn't need to keep holding onto (e.g., records for bank accounts that had been defunct for years, and so on).