Everyone is still talking about registered birth surnames.
In England & Wales there were NO registered birth surnames until 1969!
This is absolutely correct, and is one of the things I discuss at length when giving talks on the subject (as I have done twice this week). It is something very important to understand when searching birth indexes.
Along with it, you also need to remember that the birth register entry (the only original document) and any certificates produced from it are two very different things.
A birth register entry in E/W doesn't show any surname for the child before the major changes made in 1969. Before that column two is headed "Name, if any" and anything written there are the forenames of the child. The change came in the Registration Act of 1968 which now included the phrase
"...the surname to be entered shall be the surname by which at the date of registration of the birth it is intended that the child shall be known ..". Before that there was no indication of any "registered surname".
As there was no surname for the child, this was a problem for the GRO indexers - how do you make an index for the births ? The answer is that births are actually indexed under one (or both) of the named parents' surnames depending on their marital status..
If both parents are named and married, then it will be indexed under the father's surname. If there is no father named it will be indexed under the mother's surname. If both are named but not married it will be
indexed twice, appearing under each surname. If either parent has more than one surname shown ( e.g. "otherwise SMITH), it may be indexed under that as well*.
These conventions would also be followed when completing a "Short form certificate", and on the "Certificate of Registry of Birth", which preceded it. A full birth certificate, which is a direct copy of the register entry, and has always been available as a "paid for extra", doesn't give a surname.
After 1969, the informant was asked to specify the surname of the child ( Space 2 was now headed "
Name and surname" and the surname should be shown in capitals) and things become a little clearer, although double indexing for children born illegitimately still applied.
The rules in Scotland have always been different.
*note that the new GRO On-line Index uses a slightly different set of indexing rules so the results when searching that can, and often will, be different to the results you might get on FreeBMD or similar.