UK and Irish publishers are obliged by legal deposit to send a copy of all new publications, including serial titles, to the BNB for listing.
In 1981 production was transferred to Novello House on the corner of Wardour Street and Sheraton Street (adjacent to the British Library's then Central Administration offices), and in 1992 from London to the British Library's northern site on the Thorp Arch Trading Estate near to Boston Spa where it became the National Bibliographic Service.
However publications of publishers in the United Kingdom and the Republic of Ireland were included as these were subject to the copyright deposit law.
BNB's first intake was classified using the (then current) 14th edition of the Dewey Decimal Classification (DDC) but it was considered to be inadequate in specificity, currency and consistency to express the range of subjects to be found in the year's expected intake of around 15,000 items.
The colon and slash were borrowed from the Universal Decimal Classification and a suffixed [1] (assigned a filing value between zero and one) was used to extend the specificity of more general DDC numbers by adding faceted text extensions following Ranganathan's PMEST (Personality / Matter / Energy / Space / Time) order.
From January 1974, BNB adopted a new indexing system: PRECIS (PREserved Context Indexing System) which was developed by Derek Austin out of research by the Classification Research Group into the theoretical basis for a new general classification scheme.