I think that PIN (the 5 digit one) is used by TurboTax and not the IRS.
Here is a little more info. about it I found.
https://ttlc.intuit.com/community/taxes/discussion/pin-code-in-turbotax/00/3270245
Still seems kind of fuzzy about what that PIN is for and whether or not you need to keep it and what happens if you change it and whether there is any advantage to security if you DO change it.
Maybe they use it if you need to contact them about your filing for some reason or about your return?
I keep a record of it but it won't be convenient for me to find so if I need it I want to have it ready in advance when I go through the filing process. But apparently I can either use the number that is already in there or change it. And apparently as long as I use TurboTax next year it will fill in that field with whatever I used this year.
