Re-registering a birth after marriage

[Sparklemummyx0x0x]

A few weeks ago I was talking to a school mum about random inheritance stuff and she told that if a couple have a child and get married afterwards, they need to re register her birth as a child of their marriage.

My DB and SIL recently had their second child (after marrying) and when registering her last week they asked the registrar and she confirmed this was true.
My DB is the named father and my DN had his surname anyway. The only difference would be the change of my SIL surname.

According to the gov website it is a requirement. But is it a legal requirement? What are the reasons for doing or the consequences of not doing it?
I wasn't told at my DS registration and practicality all of the people I know have never heard of this either.

Thanks

Sorry I meant my DB and SIL first child (before marrying) has his surname on her birth certificate. The only difference if they were to re register would be my SIL surname.

Yes, it's a legal requirement.

I suspect it's only still on the books because no-one's got round to abolishing it.

It makes no difference to inheritance (except perhaps some inherited titles).

You can be fined for disobeying this law. The fine hasn't been increased - think it is still one guinea

Meditrina is right that the fine hasn't been increased since 1976. It is actually £2. I'm sure that has you quaking in your boots!

Rats! Out by a whole 19 shillings!