Extended SIC Codes (SIC 6-digit)
SIC codes are four-digit industry classification codes used to identify a business establishment’s primary activity. Extended six-, seven-, and eight-digit SIC codes provide more detailed industry categories, but these extensions are developed by private data providers and are not part of the official U.S. government SIC system.
The Standard Industrial Classification system organizes businesses into industries according to the products they produce, the services they provide, or the primary activities they perform. It creates a consistent framework for identifying and comparing companies engaged in similar types of business.
SIC codes continue to be used by businesses, financial institutions, government agencies, researchers, marketers, compliance teams, and commercial data providers for purposes such as:
- Business and industry research
- Market segmentation and business list targeting
- Risk, compliance, underwriting, and credit analysis
- Economic and employment analysis
- Company database organization and enrichment
- Industry benchmarking and competitive analysis
- Reviewing historical government and regulatory data
Although the North American Industry Classification System, or NAICS, replaced SIC for many current U.S. federal statistical programs, SIC codes remain widely used in commercial business databases, financial systems, regulatory filings, legacy applications, and historical datasets.
How SIC Codes Are Structured
The official SIC system uses four-digit codes. Each digit adds another level of industry detail:
- Division: A broad segment of the economy
- Major Group: A general industry category
- Industry Group: A more specific group of related activities
- Industry: The official four-digit SIC classification
For example, SIC 5812 — Eating Places is an official four-digit industry classification covering establishments primarily engaged in preparing meals, snacks, and beverages for immediate consumption.
Within a commercial business database, that broad industry may be divided into more detailed categories such as full-service restaurants, fast-food restaurants, cafeterias, pizza restaurants, or other specialized eating establishments. These narrower categories help users identify specific types of companies that may otherwise share the same official four-digit SIC code.
Users can review the complete classification structure through the SIC Code Directory or search by business activity using the SIC Code Lookup.
What Is a Six-Digit SIC Code?
A six-digit SIC code is an extended commercial classification built beneath an official four-digit SIC industry. The first four digits generally correspond to the official SIC code, while the additional digits identify a more specialized type of business activity.
The official U.S. SIC classification system ends at four digits. Six-digit, seven-digit, and eight-digit SIC classifications are therefore not official government codes. They are proprietary extensions created by business information companies to provide greater industry detail.
Extended SIC codes can be useful when a four-digit industry includes several distinct types of businesses. The added detail may help organizations:
- Identify niche markets
- Create more precisely targeted business lists
- Separate related but operationally different company types
- Improve industry segmentation within a database
- Analyze specialized products, services, or customer groups
Because extended SIC systems are privately maintained, the exact code structure and definitions may differ between data providers. Users should review the definition attached to an extended code rather than assuming that every provider uses the same six- or eight-digit classification.
SIC Codes Compared With NAICS Codes
SIC and NAICS are separate industry classification systems. SIC codes contain four official digits, while current U.S. NAICS codes can contain up to six digits.
NAICS provides greater structural detail for many modern industries and is the primary classification system used by U.S. federal statistical agencies. SIC, however, remains important because it is still embedded in many commercial databases, financial systems, regulatory records, and historical datasets.
SIC-to-NAICS relationships are not always one-to-one. A single SIC code may correspond to several NAICS codes, and one NAICS industry may include businesses previously classified under multiple SIC codes. For that reason, a code should not be selected solely through an automated crosswalk.
The most accurate classification should be based on the establishment’s primary business activity. Users can compare classifications through the SIC-to-NAICS Crosswalk or request assistance through Find My SIC and NAICS Codes.
Why Accurate SIC Classification Matters
An SIC code affects how a business is grouped, researched, compared, and targeted. An inaccurate code can place a company in the wrong industry segment and reduce the quality of business research, list building, risk analysis, compliance reviews, and database reporting.
Accurate classification helps organizations:
- Find companies that perform a specific type of work
- Measure the size and composition of an industry
- Compare companies with relevant industry peers
- Improve sales and marketing targeting
- Support compliance, underwriting, and due-diligence processes
- Maintain consistent industry data across internal systems
The correct SIC code should reflect what the establishment primarily does, not simply the company name, a secondary service, or one product it happens to sell.
Official SIC Sources and Extended Classifications
Official four-digit SIC definitions originate from the U.S. Standard Industrial Classification system. These definitions provide the foundation for classifying establishments according to their primary economic activity.
SICCODE.com combines official SIC classifications with extended industry categories, corresponding NAICS codes, crosswalk information, and commercial business data. Extended classifications are used to provide additional detail where an official four-digit industry is too broad for specialized research or business targeting.
SICCODE.com has supported industry classification and business data research since 1998, helping organizations identify SIC and NAICS codes, understand relationships between classification systems, and locate companies within specific industries.
Frequently Asked Questions
Are six-digit SIC codes official?
No. The official U.S. SIC system ends at four digits. Six-, seven-, and eight-digit SIC codes are extended classifications developed by private data providers.
Is SIC still used?
Yes. Although NAICS replaced SIC for many federal statistical purposes, SIC remains widely used in commercial databases, financial systems, regulatory records, underwriting, compliance, marketing, and historical research.
What is the difference between SIC and NAICS?
SIC is an older four-digit classification system, while NAICS is a newer system that provides classifications of up to six digits. The two systems organize industries differently, so direct conversions are not always exact.
How do I find the correct SIC code?
Identify the establishment’s primary business activity and compare it with the definition and exclusions for the most relevant SIC industries. When several codes appear possible, classification should be based on the activity that best represents the establishment’s principal source of business.