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UK National Agency for MARC Organization Codes

How to obtain a MARC organization code

  • If your organization does not have a MARC organization code, please download this form (Word format 29KB) and send your request to uk-isilmarc@bl.uk. We will assign a MARC code if you are eligible.
  • If you are unsure about whether your institution or a particular sub-unit of your institution already has a MARC code or you would like further information, please e-mail uk-isilmarc@bl.uk.

Requests for a MARC code for one organization will be processed within a few days.

If you require codes for more than one organization, or for multiple sub-units of one organization, this processing will take longer depending on the overall number and will be assessed on a case-by-case basis. Please contact us at the above e-mail address to discuss.

What are MARC organization codes?

MARC organization codes (formerly known as NUC codes) represent names of libraries, other kinds of organizations or sub-units of organizations that need to be identified in the bibliographic environment.

The British Library is responsible for the assignment of MARC codes for organizations in the UK, together with Crown Dependencies and Overseas Territories from the Library of Congress.

The British Library also assigns ISILs, which are based on MARC codes, to institutions in the UK and its dependencies. The responsibility for assigning MARC organization codes to institutions in the Republic of Ireland resides with the Library of Congress.

Directory of MARC codes for UK organizations

Check your MARC organization code in the directory, which is updated monthly.

The data is distributed under a Creative Commons CC0 1.0 Universal Public Domain Dedication licence. For further details about our terms and conditions, please see here.

Background information

MARC organization codes are 8-character variable length codes; this may include a dash. Whilst the codes include uppercase and lowercase characters in order to be more human-readable, they are case-insensitive.

They are used in whatever context requires an institutional identifier, for example in MARC bibliographic records to identify the organization creating or modifying a record; in systems reporting library holdings and in various types of cooperative projects. Although the Library of Congress has taken the lead in the assignment of MARC codes, generally speaking MARC codes are nationally based. The ISIL takes advantage of these nationally-based codes to create an international identifier.

Further information about MARC organization codes is available from the website of the Library of Congress.


For further information please contact:

The British Library
Metadata Standards
Boston Spa, Wetherby
West Yorkshire
LS23 7BQ
United Kingdom

Tel: + 44 (0) 1937 546124
Fax: + 44 (0) 1937 546586
Email: uk-isilmarc@bl.uk