I think that's true for Social Security numbers in France/US, and National Insurance numbers in UK. About 15 years ago, after working in Germany I came back to

I think that's true for Social Security numbers in France/US, and National Insurance numbers in UK. About 15 years ago, after working in Germany I came back to France for a couple of years, the country where I was born / assigned a number at birth / following a similar pattern with the year in the code. My health insurance from Germany did not transfer according to EU rules or something, at least that's what the regional French National Security told me. The way they got me out of the Kafkaesque situation was to give me a "temporary" social security number, like they would give a foreign immigrant, and have it revert back to my "normal" number after 3 months. At some point I had "two" national security numbers. It was a real mess to fix the whole thing afterwards as you can imagine, and considered I left the country only after a couple of years, I wonder why I even bothered.