NAICS Classification & Reference Center
The NAICS Classification & Reference Center is SICCODE.com’s organized library for NAICS definitions, structure, history, FAQs, governance guidance, and code lookup tools. Use this hub to explore NAICS from the top-level hierarchy down to individual code pages—then verify selections using included/excluded activities, examples, and parent hierarchy context.
Open NAICS Code Lookup / Directory or review How to Choose the Correct NAICS Code.
Authority & governance signals
On this page
- Scope and principles
- Evidence inputs used for NAICS assignment
- How SICCODE.com resolves NAICS assignment decisions
- Methodology in action (examples + deep dive)
- Additional classification scenarios
- Methodology performance metrics
- Human review & governance boundaries
- Quality checks and explainability
- NAICS revision cycles & versioning
- When to defer or use agency guidance
- FAQ
Scope and principles
SICCODE.com provides a reference layer for NAICS that emphasizes clarity, consistency, and audit-ready rationale. NAICS assignment is treated as a governed interpretation process, especially for businesses with multi-activity operations or ambiguous public descriptions.
Core principles
- Primary activity focus: classification aligns to the business’s primary activity as described and evidenced.
- Hierarchy consistency: selections respect the NAICS structure from sector to national industry.
- Explainability: decisions should be justifiable using observable business signals.
- Stability over time: avoid unnecessary churn; changes should reflect evidence or NAICS revision cycles.
What this page is not
- Not a replacement for official NAICS publications.
- Not a guarantee of eligibility for any specific program or procurement requirement.
- Not an instruction to self-select codes without validating included/excluded activities.
Evidence inputs used for NAICS assignment
NAICS classification is strongest when it is grounded in verifiable signals about what a business actually does. SICCODE.com uses a governed review approach that can incorporate multiple sources of evidence where appropriate.
Common evidence signals
- Company descriptions and activity statements (public-facing)
- Products/services offered and operational keywords
- Industry terminology and customer market positioning
- Operational context and activity mix (when available)
Reference anchoring (why the 6-digit level matters)
- NAICS hierarchy alignment (Sector → Subsector → Industry Group → Industry → National Industry)
- Included vs excluded activity logic on code pages
- Parent-child fit checks to reduce misclassification drift
Correct vs. drift (quick example)
Correct33 (Manufacturing) → 333 (Machinery) when the establishment’s primary activity is producing machinery (manufacturing output).
Drift errorKeyword “Pump” pushes to 333 (Manufacturing), but the establishment actually distributes pumps as a trade model (for example, 423 Wholesale).
How SICCODE.com resolves NAICS assignment decisions
Many businesses appear to match multiple NAICS codes. When ambiguity exists, SICCODE.com applies a structured decision approach designed to improve consistency.
Decision rule of thumb: prefer the code that best fits the primary revenue-generating activity and the most specific NAICS definition that matches the business’s actual operations.
Resolution workflow
- Candidate identification: identify likely codes based on business activity evidence.
- Hierarchy validation: confirm each candidate fits the correct parent structure.
- Included/excluded confirmation: verify the business’s activity is included and not explicitly excluded.
- Specificity selection: choose the most specific defensible code consistent with the evidence.
- Documentation and review: record rationale and apply expert review for edge cases when needed.
Methodology in action: examples + deep dive
The examples below show how a governed, establishment-level approach resolves common ambiguity patterns that often produce inconsistent NAICS results across vendors. These are reference examples designed to illustrate decision rules and stability controls.
Definition
Establishment: a single physical location where business is conducted or services are performed. NAICS assignment is typically intended to reflect the primary activity at the establishment level (not a parent corporation’s umbrella description).
Example 1: Resolving multi-activity ambiguity
Multi-activity businesses are a common source of NAICS inconsistency. Keyword-only approaches often over-weight branding language (for example, “consulting”) while under-weighting the primary operational activity. The example below shows how governed interpretation improves stability.
The case: “Solar Solutions & Consulting Group”
The business installs solar panels, offers energy efficiency consulting, and sells solar components online.
Governed resolution process
- 1) Candidate identification: identify candidates for installation, consulting services, and retail/e-commerce based on activity signals.
- 2) Primary activity determination: prioritize the primary value-adding activity using observable signals (service emphasis, operational keywords, offering footprint).
- 3) Hierarchy alignment: validate parent fit to avoid drifting into adjacent service categories.
- 4) Included/excluded check: confirm that the primary activity is covered and not explicitly excluded into a nearby code.
- 5) Documentation: record the rationale and note secondary activities to reduce churn if marketing language changes.
Outcome (what is produced)
Primary NAICS selection: NAICS 238210 (installation-focused illustration)
Secondary activities recorded: consulting and online component sales noted as secondary/supporting functions.
Governance note: Documenting secondary activities helps keep the primary NAICS code stable even if branding shifts toward “consulting” or “technology” language.
Deep dive: how a “near-neighbor” decision gets made (candidate codes, boundaries, and why-not logic)
Real classification decisions often involve “near-neighbor” codes that look plausible at a glance. A governed approach makes the decision explicit: what was considered, what was rejected, and why.
- Step A — Generate candidates: create a short list across the likely activity types (installation, consulting/professional services, and retail/e-commerce).
- Step B — Validate parents: confirm each candidate rolls up to the expected sector/subsector based on the operational reality.
- Step C — Boundary check: compare the business’s “what we do” statements against each candidate’s scope notes and included/excluded logic on the NAICS code page.
- Step D — Decide “primary”: use observable signals (service footprint, emphasis, operational language, and delivery model) to avoid being over-led by marketing claims.
- Step E — Record why-not: document why the near-neighbor code was rejected (example: the rejected code is a better fit for a different activity model, or it excludes key parts of the observed operation).
If you need a stricter, program-specific interpretation, defer to the program’s guidance and verify against the exact NAICS definitions used by that agency or contract.
Example 2: Resolving vertical integration (manufacturing + wholesaling/retailing)
Vertical integration occurs when a business operates across multiple stages of a supply chain. Without governance, these businesses are often misclassified into Merchant Wholesalers or Retail Trade based on channel language rather than establishment activity.
The case: “Apex Industrial Sealing Corp”
The business designs and manufactures custom rubber gaskets in a factory setting. In addition, it maintains a warehouse operation that distributes both self-manufactured products and third-party industrial seals, along with a limited on-site retail counter for trade customers.
Governed resolution process
- 1) Establishment-level assessment: confirm whether manufacturing, warehousing, and retail activity operate as one integrated establishment.
- 2) Primary activity determination: determine the primary value-adding activity using observable operational evidence rather than channel terminology.
- 3) NAICS rule application: when manufacturing is significant and occurs within the same establishment as wholesaling or retailing, classification is generally anchored to Manufacturing.
- 4) Code selection: select the most specific defensible manufacturing code consistent with the activity scope and hierarchy.
- 5) Secondary activity documentation: document distribution as secondary to prevent sector drift over time.
Outcome (what is produced)
Primary NAICS selection: NAICS 326291 (illustrative manufacturing-anchored example)
Secondary activities recorded: wholesale distribution and limited retail counter documented as secondary activities.
Governance note: Governed interpretation anchors classification to the primary value-adding activity (manufacturing) and records downstream channels as secondary to preserve stability.
Additional classification scenarios
These scenarios commonly produce inconsistent NAICS assignments across vendors. Use the same governed approach: define the establishment activity model, generate near-neighbor candidates, then validate boundaries with included/excluded logic.
Franchises (franchisor vs franchisee)
- Franchisee locations: classify based on what the local establishment does (for example, operating a restaurant or providing a service).
- Franchisor operations: may align to separate activities such as licensing, brand management, or support services.
- Governance tip: don’t inherit the franchisor’s NAICS onto franchisee locations without establishment-level evidence.
Digital / platform businesses
- Marketplace vs direct seller: the activity model differs (operating a platform vs selling inventory).
- Hybrid models: record secondary activities to prevent drift when the sales mix changes over time.
- Governance tip: treat “platform” as a business model claim and validate the operational reality (what is delivered, by whom, and how revenue is earned).
Seasonal / multi-season operations
- Primary activity over the cycle: determine what dominates across the reporting period you care about (annual, seasonal, contract-based).
- Stability control: document the seasonal mix so classification doesn’t churn month-to-month based on marketing updates.
Holding companies vs operating units
- Holding entity: classify the holding activity (not the operating subsidiaries’ industries).
- Operating establishments: classify each establishment by its primary activity.
- Governance tip: avoid “roll-up contamination” where a parent’s sector is mistakenly assigned to all child locations.
Methodology performance metrics
“Governed” claims are strongest when they are measurable. SICCODE.com’s validation should be reported as a small set of repeatable metrics that can be audited internally and compared across time. If you maintain published benchmark results, place the detailed figures on the relevant benchmark page and summarize the headline KPIs here.
Recommended metrics to publish
| Metric | What it shows | How to measure |
|---|---|---|
| Review change rate | How often an initial assignment is corrected after review (a proxy for review value). | Track “initial → final” changes for sampled or production-reviewed cases. |
| Inter-rater agreement | Consistency between researchers on ambiguous cases. | Double-code a sample and report agreement (and how disagreements are adjudicated). |
| Boundary error rate | How often assignments cross a sector/subsector boundary incorrectly. | Parent-child sweep + targeted audits on high-confusion boundaries. |
| Drift rate | Stability across time (how often codes change without evidence/revision triggers). | Measure churn over defined windows; require a logged trigger for each change. |
If you publish these metrics, include the evaluation window, sample definition, and whether results reflect a specific NAICS vintage (e.g., 2022).
Human review & governance boundaries
Governance is not the absence of judgment—it is the control system around judgment. This page describes a reference workflow; operational classification decisions should include clear triggers for escalation and documented adjudication for ambiguous cases.
What “human review” means here
- Evidence-first: reviewers apply observable signals and hierarchy checks before choosing between near-neighbor codes.
- Edge-case escalation: ambiguous or high-impact cases should be escalated to additional review.
- Adjudication: disagreements are resolved by referencing boundary logic (included/excluded rules) and establishment-level activity fit.
Oversight reference: the SICCODE.com Industry Classification Review Team.
Where governance ends and discretion begins
- Governance controls: candidate generation, parent-child alignment, boundary validation, documentation, and change control.
- Judgment zone: determining which activity is primary when signals conflict or revenue mix is unclear.
- Risk control: when the “right” answer is genuinely unclear, document uncertainty, record alternatives considered, and apply a stability rule (don’t churn without new evidence).
Quality checks and explainability
NAICS assignment should be consistent and explainable. Quality checks focus on reducing drift, preventing category inflation, and maintaining stable classification logic across similar businesses.
Consistency checks
- Parent/child alignment check (structural fit)
- Duplicate intent check (avoid redundant or overly broad selections)
- Outlier detection against comparable business activity profiles
Explainability outputs
- Clear “what this code covers” logic on code pages
- Included vs excluded activity clarity
- Examples and contextual notes for ambiguous terms
Use these guides when you need consistent, establishment-level decisions, clear boundaries, or defensible NAICS use in programs and compliance workflows.
NAICS revision cycles & versioning
NAICS is reviewed on a 5-year cycle to keep the classification current with changes in the North American economy. Maintaining data integrity requires a revision-aware approach so longitudinal reporting remains comparable across versions (for example, 2017 vs 2022 and the upcoming 2027 cycle).
Official revision references (external)
These are official public references used for understanding revision schedules and adoption timing.
How to navigate revision cycles
- Determine the base year: identify which NAICS vintage your program, reporting system, or contract requires (e.g., 2017 vs 2022).
- Use the 6-digit check: always verify at the 6-digit National Industry level—this is where boundary changes most often appear.
- Stability rule: don’t change codes unless triggered by new evidence, a defined revision adoption, or an error correction process.
Implementation & stability controls
- Map to the current standard: crosswalk legacy codes to current definitions when your system adopts a new vintage.
- Document rationale: record the inclusion/exclusion or boundary logic that triggered the update.
- Change control: keep timestamps and approver context to prevent “silent drift.”
Use this template to document a revision-driven change in an internal system (CRM, ERP, warehouse, master data).
- Record ID / establishment: (identifier + location context)
- NAICS vintage: (from 2017 → to 2022, or your adopted vintages)
- Old code: (6-digit) · New code: (6-digit)
- Trigger type: revision adoption / evidence update / error correction
- Boundary rationale: what inclusion/exclusion or scope change caused the shift
- Secondary activities: documented (yes/no) + short notes
- Approver: name/role · Date: timestamp · Notes: links to evidence
For revision planning, use a documented change-control workflow and record the trigger for any NAICS code update.
Use this checklist when reviewing your database to ensure classifications are defensible and revision-ready.
1) Version identification
- Does your database store the NAICS year (vintage) as a metadata field (e.g., 2017 vs 2022)?
- Have you identified records still using codes that were changed or removed in your adopted vintage?
2) Primary activity validation
- Is the code anchored to the establishment primary activity (not a parent-company umbrella category)?
- For multi-activity locations, is there a recorded rationale for why the chosen 6-digit code was selected over adjacent options?
3) Hierarchy & consistency
- Parent-child sweep: does the 6-digit code correctly roll up into the correct 2-digit Sector?
- Catch-all inflation check: are too many records assigned to “All Other / Miscellaneous” style codes that should be reviewed for specificity?
4) Revision readiness
- Audit trail: do you have a timestamped log of when a NAICS code was changed and who approved it?
- Crosswalk mapping: for longitudinal reporting, do you maintain mapping logic to compare historical vintages against current definitions?
When to defer or use agency guidance
Some scenarios require stricter rules than a general reference workflow. In these cases, treat NAICS selection as a compliance decision and defer to the controlling authority.
Defer to program / agency guidance when
- A government program, contract, or filing specifies a NAICS code (or a specific NAICS vintage) as a requirement.
- The program has its own definitions, eligibility rules, or “dominant activity” rules beyond standard NAICS interpretation.
- You are classifying for legal/regulatory purposes where penalties apply for misclassification.
Do your own establishment assessment when
- Revenue/activity mix is unclear or rapidly changing (for example, a pivoting business model).
- Multiple locations have materially different primary activities.
- Public descriptions are not reliable indicators of operations (branding is ahead of reality).
This page is a classification reference and governance guide. It is not legal advice and does not override agency-specific rules or official program requirements. For high-stakes uses, document your evidence and apply your organization’s review and approval process.
FAQ
- Is SICCODE.com an official NAICS publisher?
No. SICCODE.com provides a reference layer aligned to the official NAICS framework to help users interpret and apply NAICS consistently. - Why do businesses match multiple NAICS codes?
Many organizations operate multiple activities. NAICS assignment typically reflects the primary activity, with hierarchy and included/excluded logic used to resolve ambiguity. - How do you handle cases where two codes seem equally plausible?
Use a near-neighbor comparison: validate parents, check boundary logic (included/excluded), document why-not reasoning, and apply stability controls so the code does not churn without new evidence. - How do I confirm a NAICS code is the right fit?
Compare candidate codes using the code page’s coverage notes, included vs excluded activities, examples, and parent hierarchy context. Start at the NAICS directory. - Does NAICS change over time?
Yes. NAICS is reviewed on a scheduled cycle and revisions can adjust definitions and boundaries. A governed approach helps keep classifications stable and defensible across updates. - When should I defer to agency-specific guidance?
When a program, contract, or filing specifies a NAICS code or vintage, or when eligibility/compliance depends on the classification. Document your evidence and follow the controlling authority’s rules.