does a SIN in Ontaio get de-activated? if yes, why and who does it (CRA?) . and does it need a valid PRC to activiate it again?
It has nothing to do with Ontario, it's a federal thing (either CRA or employment ministry). SINs can be put into 'dormant' status, which seems to mean that access is limited and (the critical part) no transactions that benefit from the SIN (unemployment, pension) can be carried out - that's to protect against fraud. It does NOT seem to formally mean that it cannot be used to work (by the SIN holder, of course), but CRA may contact the employer (although not clear how often this has actually happened or what the contact consists of).
Yes, the dormant status flag can be removed by means of showing a PRC.
Again, the 'collision' is that it remains unclear whether this would stop one from working (it's a distinct issue from that for those who never had a SIN). My view is - legally it cannot. But employers don't like getting contacted by the agencies responsible for SIN.
Note, there IS a logic for CRA/employment ministry to check with employers about dormant SINs being used - the potential for fraud by employers by using SINs of people who have left Canada forever, a sort of 'dead souls' scheme, to reduce their taxes. This kind of stuff would be outright fraud, and is a plausible reason for CRA/Employment to have and use a dormant SIN approach. But in theory that could be resolved with CRA by simply showing identification - this person is actually working etc. We just don't have concrete info here.
What we have, mostly, is people with potential or real dormant status who can't get it removed (albeit somewhat uncertain consequences), as well as occasional cases of someone who can't get a SIN and never had one, and in both cases Service Canada requires PRC to fix it.
