Structure of the Classification Number

The SuDocs Classification Number consists of a class stem and a suffix. The class stem is a general designation used to bring related publications together. The suffix uniquely identifies a publication and differentiates it from all others classified under the same stem.

The suffix consists of a book number, and sometimes additions to the book number. For numbered publications, the book number is usually derived from the numeric designation appearing on the publication. For unnumbered publications, the book number is usually derived from a word in the title using a Cutter number.

A fundamental rule in SuDocs classification is that each publication is assigned a unique classification number. In cases where an identical number would apply, a word, abbreviation, or number is added to the book number to differentiate the two. If a publication consists of multiple parts or issues, each discrete piece receives its own unique extension to the book number.

A Superintendent of Documents classification number begins with a capital letter or letters representing a Government department or agency; capital letters are used for all letters in Superintendent of Documents classification numbers:

A  (Department of Agriculture)

The letters are followed by a number representing the agency as a whole, or a subordinate office. This is followed by a period:

A 13. (Forest Service)

After the period, there is a number designating the series or serial title, or category of the publication, followed by a colon:

A 13.150:  (Southern Research Station: General Publications)

In this example, A 13.150: constitutes the class stem. The class stem alone shows that the publication in this example is a general publication issued by the Department of Agriculture, Southern Research Station.

The letters and numbers after the colon represent the individual publication:

In this example, W 64 is the book number.

Spacing is critical for the proper construction of the class number. A space must be inserted between letters and numbers in the class number unless there is intervening punctuation.

Formatting examples:

Incorrect SolutionCorrect formatting
A 93.2:AF8 Add a space between F and 8 A 93.2:AF 8
C 55.22/ 3:SE 1 Delete the space after the slash symbol C 55.22/3:SE 1
D5.317:616(717-5)A Add a space after D; before, after parentheses D 5.317:616 (717-5) A
D 101.11:9-2330-363-14 & P Remove spaces between 4&P D 101.11:9-2330-363-14&P
I 49.44/2: AS 3/4/2016 Delete the space after the colon I 49.44/2:AS 3/4/2016
  • Parentheses are the only exception to the spacing rule. One space must be inserted before and after a parenthesis, unless there is adjacent punctuation.
  • No spaces precede or follow symbols, such as the ampersand (&) or slash.
  • In classification numbers, roman numerals (I, II, III) should be converted to Arabic numerals (1, 2, 3).

Libraries can construct their own Superintendent of Documents classification numbers according to the principles outlined here. For documents falling in existing classes, find the class stem in the List of Classes. Add a Cutter number, date, or series number after the colon and an arbitrary designation such as “X” at the end to indicate that it is a locally assigned number.

Government publications are classified after they are received by LSCM; publications not received are not assigned classification numbers by LSCM.

Sorting in SuDocs Order

SuDocs classes are arranged alphabetically based on the leading letter(s). The number between the period and colon is a whole number (ex. HS 1.2: comes before HS 1.15:). After the colon, the hierarchy of sorting is as follows:


In both the class stem and the suffix, an empty space will file before a space that has a letter or number (i.e. ‘nothing’ before ‘something’). The ‘nothing’ aspect includes spaces and punctuation, with the exception of the colon. This is illustrated in the following list with the example of Y 4.EC 7:S.HRG.110-646 preceding Y 4.EC 7:SA 9/2.

Example of a SuDocs Sort

A 13.2:T 73/4
A 93.2:N 95/3
A 93.73:76
A 93.73:89
A 93.73/2:62
C 13.58:7564
C 13.58:7611
HE 20.4002:AD 9/2
HE 20.4002:AD 9/5
HE 20.4002:F 94
L 36.202:F 15/2
L 36.202:F 15/2/980
L 36.202:F 15/3
Y 1.1/7:109-118
Y 1.1/7:109-131
Y 1.1/7:110-6
Y 1.1/7:110-20
Y 4.EC 7:C 73/7
Y 4.EC 7:C 73/10
Y 4.EC 7:S.HRG.110-646
Y 4.EC 7:SA 9/2
Y 4.EC 7:SCH 6
Y 4.EC 7:SE 2