There are also those who never officially registered at a parish ever, including those (very many) who were baptized at a parish different from their parents' parish and were never officially entered on the rolls of either.
I have been a Catholic all my life and to my knowledge, never registered, even though my sons and daughter were all baptized and confirmed.
Perhaps doing any of those things triggers "registration" of a sort, but if there is any requirement for registration, I am unaware of it. Mind you, no ID was ever required when I attended masses...