I have read in other posts that an old SIN (mine was last used 25 years ago) "hibernates" after 5 years. Is it mandatory to reactivate an existing number, no matter how old it is (does it take long?), or would there be any advantage (not that I can think of any....other than in a vain attempt to change one's identity!) in applying for a new one? It may even be an offence to apply for a second SIN?

I returned to Canada after many years and my SIN had been put into hibernation. When my husband and daughter applied for their cards there was no problem but the office said I would have to be interviewed in order for my SIN to be reinstated, they wouldn't issue a new number. Felt like a criminal being interviewed (why did you leave the country, is this really your husband etc.) but no problem they issued a new card with married name a month later.

Came back after 15 years away and didn't even get a new card, just told to use my old SIN and have a nice day.

No interview and no issues. Been back 18 months had four jobs and done a tax return all with my original SIN. Until this thread didn't know there could have even been an issue.

I would try to use your old one but you can ask at Servicecanada centre.

cheers

Wow, I never heard of this. I was in the UK for 24.5 years. Never had any problems using my SIN on forms. Funny, I never even forgot the number, nor did I ever lose my card. It was never my intention to come back either. I've been back 7 years now.

Same here. I was PR here when I left for what turned out to be 8 years in Germany; came back in 1993 and never even asked about a new SIN.

Not a problem. Of course if you return as a PR having previously been here on a TWP, that's a different matter.

That's only typical Canada, I must say. Always this questioning and distrust.

Not using your SIN doesn't automatically mean that you really left the country. You could also be in Canada, have lot's of money, but no income, not even interest, just living of your savings. It works for a while and is entirely possible.

By my understanding hibernation just means some form of "inactivity", not stating what should be done to use it again, no matter if it is 5 or 10 years. After all, if you use it again, you're paying taxes again, and have an income. And Canada certainly won't mind you paying taxes :-)

No it's not. You'd still have to file a tax return, identified by your SIN.