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020 - International Standard Book Number (R)


First IndicatorSecond Indicator
# - Undefined
# - Undefined

Subfield Codes
  • $a - International Standard Book Number (NR)
  • $c - Terms of availability (NR)
  • $q - Qualifying information (R)
  • $z - Canceled/invalid ISBN (R)
  • $6 - Linkage (NR)
  • $8 - Field link and sequence number (R)


International Standard Book Number (ISBN) assigned to a monographic publication by designated agencies in each country participating in the program. The field may include terms of availability and canceled or invalid ISBNs, such as ISBNs with invalid check digits or that are not applicable to the item being cataloged. It may be repeated for multiple numbers associated with the item (e.g., ISBNs for the hard bound and paperback manifestations; ISBNs for a set as a whole and for the individual parts in the set).
Each field contains all the information relevant to one ISBN, or if no ISBN exists, relevant to the item being cataloged.



  • Both indicator positions are undefined; each contains a blank (#).


$a - International Standard Book Number
Valid ISBN. ISBN and the embedded hyphens may be generated for display.
020##$a0914378260$qpbk.$qv. 1$c$5.00
020##$a0394502884$qRandom House$c$12.50
020##$a0877790086 :$c$10.00
020##$a0877790019$qblack leather$z0877780116 :$c$14.00
020##$a0877790124$qblue pigskin$c$15.00
020##$z0877790159$qeasel binding$c$16.00
[Five numbers associated with one catalog record. Two are valid; one has both a valid and invalid form; two are invalid.]
$c - Terms of availability
Price or a brief statement of availability and any paranthetical qualifying information about availability.
If only price information is present, data relevant to a single item is given in one subfield $c in one field 020 and data relevant to another item is given in another subfield $c in a subsequent 020 field.
020##$cRs15.76 ($5.60 U.S.)
020##$a0460044524$cRental material
020##$cFor sale ($450.00) or rent ($45.00)
020##$cFor sale ($200.00 for 3/4 in.; $150.00 for 1/2 in.)
$q - Qualifying information
A brief statement of qualifying information concerning the item associated with a number being recorded in subfield $a or subfield $z.
020##$a0394170660$qRandom House$qpaperback$c$4.95
020##$a0456789012$qreel 1
020##$z0567890123$qreel 2
020##$a9780060723804$qacid-free paper
$z - Canceled/invalid ISBN
Canceled or invalid ISBN. ISBN (invalid) and the embedded hyphens may be generated for display.
Each canceled/invalid ISBN is contained in a separate subfield $z. If no valid ISBN exists, subfield $z may be used alone in the record.
020##$z0835200028 :$c$10.00
[Two ISBN's associated with one catalog record, one of which is invalid.]
$6 - Linkage
See description of this subfield in Appendix A: Control Subfields.
$8 - Field link and sequence number
See description of this subfield in Appendix A: Control Subfields.


Qualifying Information - In displays, qualifying information may be enclosed in parentheses.
ISBN Structure - ISBN is an agency-assigned data element. ISBNs are assigned to monographic publications by designated agencies in each country participating in the program. An ISBN consists of ten or thirteen digits. The 10-digit ISBN comprises four groups separated by hyphens. (The tenth digit is a check digit used as a computer validity check; it consists of a number between 0 and 9 or an uppercase X (for the arabic numeral 10). The 13-digit ISBN comprises of five elements. Element one consists of a 3-digit EAN prefix that identifies the book industry. Element two identifies the country or language agency. Element three identifies the publisher prefix. Element four identifies the title or specific edition of a publication. Element five contains a check digit.
Procedures for validation of the ISBN by calculating the check digit and hyphenating instructions are in Information and Documentation - International Standard Book Numbering (ISBN) (ISO 2108).
Classes of ISBNs - ISBNs may be valid for the item being cataloged, or canceled, structurally invalid, or application invalid. The following conventions may be followed to select the appropriate subfield for an ISBN.
Valid ISBN: - Valid ISBN is one in which the length, structure, and check digit are correct, and the ISBN is applicable to the item being cataloged. The validity of an ISBN to a particular bibliographic item is usually related to the treatment given it by the cataloging agency in terms of the number of records involved. If a single record represents more than one manifestation, e.g., hard back and paperback, both ISBNs are valid. If a single record represents a multipart monograph, ISBNs for the set as a whole and those for individual volumes are valid. If a single record describes the main part and supplemental parts of a bibliographic item, all ISBNs for the main and the supplemental material are valid. In cases of multiple valid ISBNs in one record, appropriate qualifiers to differentiate the ISBNs are usually included. Note that during the transition from a 10-digit ISBN to a 13-digit one (2005-2007), some bibliographic agencies include both a 13-digit number and a 10-digit one for the same item in repeated 020 fields. In such cases, parenthetical qualification is not used to differentiate between the 10-digit and 13-digit ISBNs.
Canceled ISBN: - ISBN is considered to be canceled when a publisher designates it as such.
Structurally invalid ISBN: - ISBN is considered to be structurally invalid when its length or structure is incorrect or its check digit does not agree with the formula for calculating it.
Application invalid ISBN: - ISBN is considered to be application invalid for a particular record when it appears on the bibliographic item, but it is known, through research or other means, that the same number is also assigned to a different resource.
ISBN may also be considered to be application invalid if it is not directly applicable to the bibliographic item represented by a particular record. Application invalidity is usually related to the cataloging treatment employed by a particular agency in terms of the number of records involved. For example, if there is a record for a multivolume set as well as separate records for each of the volumes in the set, the ISBN for the set is considered application invalid on the records for the volumes. Only the ISBN applicable to the entity represented by a particular record is considered valid on that record.
Punctuation - Field 020 does not end with a period.
Display Constants
ISBN[associated with the content of subfield $a]
ISBN (invalid)[associated with the content of subfield $z]
- - -[embedded hyphens]
ISBN usually appears on an item with the prefix ISBN and with each of its parts separated from the other by hyphens or spaces. The initialism ISBN, the phrase ISBN (invalid), and the embedded hyphens are not carried in the MARC record. They may be system generated as display constants associated with the content of subfields $a and $z, respectively.
Content designated field:
020##$a0870686933$qv. 1$z087064302
Display example:
ISBN 0-87068-693-3 (v. 1) ISBN (invalid) 0-87068-430-2

  • This article is a Stub. It will be expanded to achieve the level of a proper encyclopedia article. 

  1. Library of Congress. (accessed October 12, 2017)



  • Written: 2017-10-12


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