When you register a kid with the JSBs for the first time do you need to bring a birth certificate?
I'm fairly sure I did when I registered my son but that was many years ago!
Wifey had to do it once when she first joined our daughter in time for my first fathers day. She's 11 now and never had to since, but I don't think it's advertised anywhere - they wouldn't even believe her apparently and had to go home to collect it despite my daughter only a few months old being with her at the time!