The Superintendent of Documents (SuDoc) number is primarily used as the unique identifier for retrieving United States Government Documents.

The numbers are based on a provenance based classification scheme derived by Adelaide Rosalie Hasse for the Government Printing Office (GPO) between 1895 and 1903.

The following table indicates the initial letters of a SuDoc number, and to which government entity it applies. Note that since this is a provenance based organization scheme that items are not grouped by subject. SuDoc numbers starting with "J" may include publications with crime statistics, or coloring books of McGriff, the Crime Dog. In both cases, the disseminating agency would be the Department of Justice.

A    Agriculture Department 
AC   Arms Control and Disarmament Agency 
AE   National Archives and Records Administration 
C    Commerce Department 
CC   Federal Communications Commission 
CR   Civil Rights Commission 
D    Defense Department 
E    Energy Department 
E 2. Federal Energy Regulatory Commission 
E 3. Energy Information Administration 
E 4. Economic Regulatory Administration 
E 5. Bonneville Power Administration 
E 6. Western Area Power Administration 
E 7. Alaska Power Administration 
ED   Education Department 
EP   Environmental Protection Agency 
FA   Fine Arts Commission 
FCA  Farm Credit Administration 
FEM  Federal Emergency Management Agency 
FHF  Federal Housing Financing Board 
FHL  Federal Home Loan Bank Board 
FM   Federal Mediation and Conciliation Service 
FMC  Federal Maritime Commission 
FR   Federal Reserve System Board of Governors 
FT   Federal Trade Commission 
FTZ  Foreign-Trade Zones Board 
GA   General Accounting Office 
GP   Government Printing Office 
GS   General Services Administration 
HE   Health and Human Services Department 
HH   Housing and Urban Development Department 
I    Interior Department 
IA   U.S. Information Agency 
IC   Interstate Commerce Commission 
ITC  International Trade Commission 
J    Justice Department 
JU   Judiciary 
L    Labor Department 
LC   Library of Congress 
LR   National Labor Relations Board 
MS   Merit Systems Protection Board 
NAS  National Aeronautics and Space Administration 
NC   National Capital Planning Commission 
NCU  National Credit Union Administration 
NF   National Foundation on the Arts and the Humanities 
NMB  National Mediation Board 
NS   National Science Foundation 
OP   Overseas Private Investment Corporation 
P    United States Postal Service 
PE   Peace Corps 
PM   Personnel Management Office 
PR   President of the United States 
PREX Executive Office of the President 
PRVP Vice President of the United States 
RR   Railroad Retirement Board 
S    State Department 
SBA  Small Business Administration 
SE   Securities and Exchange Commission 
SI   Smithsonian Institution 
T    Treasury Department 
TC   International Trade Commission 
TD   Transportation Department 
VA   Veterans Affairs Department 
X    Congress 
Y    Congress