SIC Codes Explained: History, Structure, and Concordances

Compiled & reviewed by the EntityCodes Editorial Team (Tech Labs FZ LLC) · Data verified: 2026-06-28

Standard Industrial Classification (SIC) codes are legacy four-digit numerical codes developed in the U.S. in the late 1930s to classify economic establishments by business activity.

The Structure of the Four-Digit SIC System

Although the U.S. federal government officially replaced SIC with NAICS in 1997, the 1987 SIC manual remains a vital reference in historical datasets and regulatory classifications ^[1]. The system is built around four levels of detail:

Divisions: Represented by letters A through K (e.g., Division I represents Services).
Major Groups: Two-digit codes aggregating industry groups (e.g., Major Group 73 represents Business Services).
Industry Groups: Three-digit subdivisions (e.g., Industry Group 737 represents Computer Programming, Data Processing, and Other Computer Related Services).
Specific Industries: The final four-digit code, such as SIC 7371 for Computer Programming Services.

Our database contains exactly 1,004 distinct four-digit SIC codes derived from the authoritative OSHA SIC manual ^[1].

Legacy Industrial Classification Guidelines

To support the core compliance tasks detailed in this guide on SIC Codes Explained: History, Structure, and Concordances, compliance officers and corporate attorneys must consult several legacy industrial databases. Workplace safety guidelines are based on the U.S. Occupational Safety and Health Administration (OSHA) Standard Industrial Classification (SIC) Manual. For financial reporting, public registries continue to group companies using the U.S. Securities and Exchange Commission (SEC) SEC EDGAR Filer Standard Industrial Classification Codes. Mappings between retired classes and active codes are resolved using the U.S. Census Bureau SIC to NAICS Concordance Mapping Tables. Macroeconomic indices are structured around the Federal Reserve Board (FRB) Industrial Production and Capacity Utilization G.17 Release. Employment archives are categorized under the Bureau of Labor Statistics (BLS) SIC Archive for Quarterly Census of Employment and Wages (QCEW), occupational hazard research uses the National Institute for Occupational Safety and Health (NIOSH) SIC Occupational Injury and Illness Coding Guidelines, and disclosure compliance uses the U.S. Securities and Exchange Commission (SEC) Regulation S-K Commercial Disclosure and SIC Requirements. Code lookups can be run via the NAICS Association Standard Industrial Classification (SIC) Lookup Directory. Safety oversight is legislated by the U.S. Congress Occupational Safety and Health Act of 1970 Statutory Text, and the historical development is detailed by the Office of Management and Budget (OMB) Standard Industrial Classification Manual Development History.

💡 Expert Guidance: OSHA & SEC SIC Compliance Mistake

Using a commercial SIC code for safety audits or SEC filing segments can be problematic. The SEC relies on its own specific list of 4-digit filer SIC codes, while OSHA utilizes historical 1987 industry classes for safety exemptions. Always cross-verify the specific regulatory manual's index rather than trusting private credit registries.

Deep-Dive Guides in this Category

Why Legacy SIC Codes Persist in Modern B2B Databases and Systems - Explains why four-digit SIC codes remain widespread in marketing data, risk underwriting, and historical datasets despite being legacy.
How SEC EDGAR Uses SIC Codes for Public Company Classification - A compliance guide explaining how the SEC assigns primary industrial classifications to filers and how it impacts regulatory searches.
How to Perform a SIC to NAICS Crosswalk Conversion - A technical walkthrough demonstrating how to map legacy SIC codes to modern 2022 NAICS categories using historical concordances.
OSHA Compliance and Industry Standard Industrial Classification Lookup - Details how OSHA uses legacy SIC codes to determine facility recordkeeping requirements, safety standards, and program applicability.

Frequently Asked Questions

Is the SIC manual still updated? ▾

No. The official U.S. SIC manual was last updated in 1987 and is no longer revised, but it remains active in many compliance applications.

How does a SIC code differ from a NAICS code? ▾

SIC codes are four digits long and focus on product output, while NAICS codes are six digits long and classify establishments by production processes.

Who originally developed the Standard Industrial Classification (SIC) system? ▾

The Standard Industrial Classification (SIC) system was originally developed in the late 1930s by the U.S. Interdepartmental Committee on Industrial Classification under the auspices of the Bureau of the Budget (now the Office of Management and Budget) to standardize federal economic reporting.

What is the highest hierarchical tier in the SIC taxonomy? ▾

The highest tier in the SIC taxonomy is the Division, represented by letters A through K (such as Division A for Agriculture, Forestry, and Fishing, or Division I for Services). These divisions group major industries into broad economic sectors.

How many digits are in a specific SIC industry code? ▾

A specific SIC industry code contains exactly four digits. The first two digits represent the major group, the third digit defines the industry group, and the fourth digit specifies the exact industry classification.

When was the U.S. Standard Industrial Classification (SIC) manual last revised? ▾

The official U.S. SIC manual was last revised in 1987 by the Office of Management and Budget. The federal government ceased updates to the manual when it transition to the NAICS system in 1997, leaving the 1987 manual as the final active version.

Why do insurance agencies continue to use SIC codes for risk underwriting? ▾

Insurance carriers and underwriters have accumulated decades of historical loss, accident, and liability statistics structured around the four-digit SIC codes. Re-indexing these risk tables to the six-digit NAICS framework is extremely expensive, so they retain SIC for compatibility.

What is the difference between a SIC major group and an industry group? ▾

A SIC major group is a broad two-digit category (such as Major Group 73 for Business Services), while an industry group is a more detailed three-digit sub-category (such as Industry Group 737 for Computer Programming and Data Processing) within that major group.

Does OSHA still publish the 1987 SIC manual online? ▾

Yes, the Occupational Safety and Health Administration (OSHA) maintains the complete 1987 SIC manual on its official portal as a reference tool for safety regulations, hazard assessments, and recordkeeping rules.

What does 'NEC' stand for in many SIC code titles? ▾

In many SIC code titles, 'NEC' stands for 'Not Elsewhere Classified'. These are catch-all categories used to classify business activities that do not fit into any of the specific four-digit industries within an industry group.