I'm a Dutch citizen who has previously lived in Sweden for six years, but I have since moved on. The Swedish version of what is called social security number, social insurance number, government service number, or otherwise, is the personnummer. I got a personnummer assigned shortly after arriving and registering in the country. Does this personnummer remain valid for the rest of my life, or is there some expiry? I know that my Canadian social insurance number will expire. What about my Swedish one?
I did a quick search on Skatteverket's site, and found this:
Personnumret får man av Skatteverket. Den som en gång fått ett personnummer behåller samma nummer livet ut. Det innebär att personnumret inte ändras vid t.ex. flyttning från eller till Sverige.
My (unprofessional, but I'm a native Swedish speaker) translation:
Personal numbers are assigned by Skatteverket. After being assigned a number, you keep it for the rest of your life. This means that the number doesn't change for example by moving from or to Sweden.
So no, it doesn't expire.
It seems that it remains valid for the rest of your life. I found this forum discussion, where several people confirm this:
My wife had lived in the States for 15 years when we moved back to Sweden. We just went to Skatteverket in person with all our IDs and passports with us, and she had her personnummer "reactivated" as now living permanently in Sweden and not abroad.
I'm pretty certain it is yours for life. My mother left sweden to live in UK 40 years ago, and she occasionally returns and can still use it for opening bank accounts etc.