Are SIC Codes Obsolete? How 6-Digit SIC Codes Are Still Used in B2B Marketing
SIC codes are not obsolete. While NAICS is widely used in government reporting, SIC codes remain deeply embedded in commercial databases and B2B marketing workflows. Extended SIC-style structures are often used by data providers to support finer segmentation.
Contrary to the misconception that Standard Industrial Classification (SIC) codes are obsolete, they continue to be widely used across private-sector datasets, B2B marketing systems, and legacy reporting environments. Although NAICS has become the preferred system for many government statistical and contracting purposes, SIC codes remain foundational in commercial classification and historical analysis.
Important clarification: Official U.S. SIC codes are standardized at the 4-digit level. Any 6-digit SIC (or longer) codes encountered in databases are typically vendor-defined extensions. Their definitions, structure, and coverage vary by provider.
Why SIC Codes Still Matter in B2B Marketing
Common commercial use cases
- B2B marketing databases and prospect lists
- CRM enrichment and account segmentation
- Legacy benchmarking and trend analysis
- Industry filtering in analytics platforms
Why organizations retain SIC
- Continuity with historical datasets
- Alignment with vendor-maintained taxonomies
- Faster segmentation for marketing workflows
- Compatibility with older reporting systems
The Role of Extended (6-Digit) SIC Codes
Many commercial datasets extend SIC-style structures beyond four digits to create additional subcategories. While these extensions are not standardized, they can add value when applied consistently within a single data provider’s taxonomy.
Where extended SIC adds value
Extended SIC segments can reduce over-broad targeting by distinguishing different business models that would otherwise share the same 4-digit SIC.
Key limitation to understand
Because extended SIC definitions are provider-specific, they should always be documented and used consistently within the same dataset to avoid misclassification.
Industry Example: Why Extensions Exist
The example below illustrates how a single official SIC can be subdivided by a data provider to support more precise marketing or analytical use cases.
- 4-digit SIC (Official): SIC 7371 – Computer Programming Services
- 6-digit SIC (Vendor Extension): SIC 7371-02 – Custom Software Development
- 6-digit SIC (Vendor Extension): SIC 7371-03 – Web Design Services
In this scenario, the official SIC remains the authoritative anchor, while the extended codes allow marketers or analysts to differentiate between distinct service models within the same industry group.
SIC to NAICS Cross-Walk: Best Practice
Many organizations maintain both SIC and NAICS codes using a cross-walk—a reference table that maps SIC industries to their closest NAICS equivalents. This is especially important because the relationship is not always one-to-one.
Pro tip: One SIC code may map to multiple NAICS codes (or vice versa). Best practice is to store both SIC and NAICS values in your database rather than attempting on-the-fly conversion. This preserves accuracy, auditability, and historical continuity.
For a detailed comparison and mapping considerations, see SIC vs NAICS Codes .
The Future of SIC Codes in Business Strategy
As classification systems continue to coexist, many organizations adopt a dual-system approach: NAICS for government-aligned reporting and SIC for commercial datasets, historical analysis, and marketing segmentation. When extended SIC structures are used, their definitions should be clearly documented to ensure consistent interpretation.