Your insurance number is printed on the front of your insurance card. This number also corresponds to your CERNid and consists of 5 or 6 characters, plus an extension:

CERNid followed by .0 = Principal Member (xxxxxx.0)

CERNid followed by .20 = Spouse (xxxxxx.20)

CERNid followed by .1 = 1st child (xxxxxx.1)

CERNid followed by .2 = 2nd child (xxxxxx.2)

CERNid followed by .3 = 3rd child (xxxxxx.3) ...

You can also find your CERNid on your CERN access card above the expiration date.