International Standard Book Number (ISBN)

Welsh Books Council

International Standard Book Number (ISBN)

It is essential that all books offered for sale carry an International Standard Book Number (ISBN). Without it, distributors’ and booksellers’ computer systems would not recognise a title’s existence. An ISBN (13 digits since 2007) consists of the following elements:

  • a group identifier (country or language code)
  • a publisher identifier
  • a title number
  • a check digit used by computers to verify the whole ISBN.

The ISBN should be printed on:

  • the cover of a book (adjacent to the bar code)
  • the title-verso of a book (the copyright page or reverse of the title page)
  • all advertisements, advance information sheets, catalogues, etc.

An ISBN is needed:

  • for each different binding (paperback or hardback) or format of a book, even if these appear simultaneously
  • for any book which is re-published under a new title, even if the contents remain unchanged
  • for a revised edition of a book
  • any book published on the web, even if there is no print edition
  • spoken word tapes (audio books) and CD products carrying text and graphics and primarily designed to instruct or educate (e.g. CD-ROM encyclopaedias).

No new ISBN is needed:

  • for a reprint of a book, even with a re-designed cover
  • for an imported book which already carries an ISBN
  • music products on tape or CD.

In the UK, ISBNs are allocated by the UK ISBN Agency. The Agency is managed by Nielsen BookData (, formed in 2002 after the merger of Whitaker, First Edition and Book Data. Full details about how to get ISBN numbers are available from:

UK International Standard Book Numbering (ISBN) Agency Ltd
3rd Floor
Midas House
62 Goldsworth Road
GU21 6LQ

Tel. 01483 712 215 
Fax 0870 7778714


In 2007 the ISBN was increased from 10 to 13 digits, in order to increase the ISBN system’s capacity and keep pace with the enormous growth of the publishing industry. The change brought the book trade into line with product numbering by non-book retailers (e.g. supermarkets selling paperback books). The main revisions to the system were:

  • ISBNs increased from 10 to 13 digits
  • existing ISBNs were prefixed by 978 and the final check number altered
  • the resulting 13-digit number is identical to the EAN-13 number that is encoded in the bar code
  • a 979 prefix will be introduced when the current stock of numbers is exhausted
  • publishers' identifier prefixes are not likely to remain the same for ISBNs using the 979 prefix
  • bar codes carry the 13-digit ISBN, with hyphenation, above the barcode and the EAN-13, the identical number without hyphens or spaces, below the bar code.

Copies of the new Standard, published in 2005, may be ordered direct from the International Organization for Standardization website (  ISO as ISO 2108 (Fourth edition): Information and documentation — International standard book number (ISBN). 

Help is available from the following sources:


The International ISBN Agency has published a set of guidelines and FAQs on the assignment of ISBNs to e-books. It can be found at You can also find further information in BIC Code of practice for identification of e-books and digital content at

Date last updated: 7 Aug 2019