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A business email list by SIC or NAICS code is a B2B contact list filtered by standardized industry classification codes. Instead of searching for construction companies, you select the exact code, for example NAICS 238220 for plumbing, heating and air-conditioning contractors, and then narrow the list by company size, location and job title. NAICS is the current U.S. standard. SIC is the older four-digit system that is still common in business databases and public-company filings.
Industry codes give list building a common language. They help you define who is in your market, find similar industries worth testing, exclude those that are not, and keep your CRM consistent. But a code is a proxy for what a company does, not a guarantee that it will buy from you.
This guide explains how SIC and NAICS codes work, how they differ, how to choose the right codes and level of detail, what the proposed 2027 NAICS update means, and how to avoid the mistakes that make code-based lists less accurate than they look.
SIC and NAICS codes are numeric systems that group businesses by the economic activity they perform. Each code points to an industry definition, which lets governments, researchers and marketers describe and count the same industries in the same way.
The Standard Industrial Classification (SIC) system uses four-digit codes. According to the Bureau of Labor Statistics, the 1987 SIC manual defines eleven divisions, 83 major groups (two digits), 416 industry groups (three digits) and roughly one thousand industries (four digits). NAICS was adopted in 1997 to replace SIC, but SIC has not disappeared. OSHA still hosts the 1987 SIC manual online, and SEC EDGAR filings for public companies still carry SIC codes. The BLS describes the structure in its field definitions.
The North American Industry Classification System (NAICS) was developed by the United States, Canada and Mexico so that business statistics are comparable across the three countries, and it is reviewed every five years. A NAICS code has up to six digits. In the 2022 U.S. version, the Office of Management and Budget lists 20 sectors, 96 subsectors, 308 industry groups, 689 five-digit industries and 1,012 six-digit national industries. The official lookup is on the Census Bureau NAICS site.
One detail matters for marketers. NAICS classifies establishments, meaning individual business locations, by their primary type of economic activity, and OMB states that it is developed and maintained for statistical purposes. It is widely used in business, but its definitions were not written for sales targeting.
| Feature | SIC | NAICS | What it means for list building |
|---|---|---|---|
| Code length | 4 digits | Up to 6 digits | NAICS can describe an industry in more detail |
| Structure | Divisions, major groups, industry groups, industries | Sectors, subsectors, industry groups, industries, national industries | Both let you choose a broad or a narrow level |
| Status | Based on the 1987 manual; replaced as the federal statistical standard in 1997 | Current federal standard, reviewed every five years | NAICS reflects newer and service industries better |
| Geography | U.S. system | Shared by the U.S., Canada and Mexico | NAICS is easier to use for North American campaigns |
| Where you still see it | SEC EDGAR filings, OSHA’s manual, many commercial databases and CRMs | Government statistics, SBA size standards, most modern data tools | Ask which system your provider’s records carry |
The two systems do not map one to one. The Census Bureau’s correspondence tables show, for each NAICS industry, the SIC categories or parts of categories that make it up, so one SIC code can split across several NAICS codes and several SIC codes can combine into one. If your data carries both, confirm that the industries you selected under one system line up with the other.
Each digit of a NAICS code narrows the industry. The first two digits identify the sector, the third the subsector, the fourth the industry group, the fifth the NAICS industry and the sixth the U.S. national industry, which lets each country add detail.
| Digits | Level | Example: 541511 |
|---|---|---|
| 2 | Sector | 54: Professional, Scientific, and Technical Services |
| 3 | Subsector | 541: Professional, Scientific, and Technical Services |
| 4 | Industry group | 5415: Computer Systems Design and Related Services |
| 5 | NAICS industry | 54151: Computer Systems Design Services |
| 6 | National industry | 541511: Custom Computer Programming Services |
Three sectors span a range of two-digit codes: Manufacturing (31 to 33), Retail Trade (44 to 45) and Transportation and Warehousing (48 to 49). If you filter on a single two-digit number such as 31, you will miss most of manufacturing.
These examples show how similar types of business appear in each system. They are for illustration, so always confirm codes in the official manuals before building a list.
| Industry | NAICS (2022) | SIC (1987) | Example roles to target |
|---|---|---|---|
| Offices of physicians | 621111 | 8011 | Practice administrators, practice owners, medical directors |
| Offices of dentists | 621210 | 8021 | Practice owners, office managers |
| Real estate agents and brokers | 531210 | 6531 | Broker-owners, managing brokers, agents |
| Custom computer programming | 541511 | 7371 | Founders, CTOs, VPs of engineering |
| Plumbing, heating and air-conditioning contractors | 238220 | 1711 | Owners, general managers, service managers |
| Full-service restaurants | 722511 | 5812 (Eating Places) | Owners, general managers, multi-unit operators |
| Law firms | 541110 | 8111 (Legal Services) | Managing partners, firm administrators |
| Accounting firms | 541211 | 8721 | Partners, firm administrators |
Notice that the match is not exact. SIC 5812, Eating Places, covers a wider group than full-service restaurants alone, and SIC 6531, Real Estate Agents and Managers, includes managers as well as agents and brokers. That is why a code is a starting point for a list, not the final definition of your audience.
An industry code tells you what kind of business a company is. It does not tell you how large it is, where it operates, who makes buying decisions or whether it needs your product. Used well, codes do five jobs.
A loose label such as healthcare or manufacturing hides large differences. Codes let you specify offices of physicians versus offices of dentists, or a particular manufacturing industry, so that you, your data provider and your CRM all mean the same thing. For industry-level background, see our guides to the manufacturing industry email list and the construction industry email list.
Look at the codes of your best customers, then at neighboring codes in the same industry group. A vendor serving plumbing and HVAC contractors (NAICS 238220) might test electrical contractors (NAICS 238210) because both sit in industry group 2382, Building Equipment Contractors.
Codes work in reverse too. If a broad keyword pulls in industries that are irrelevant to your offer, excluding their codes protects list quality and your sending reputation.
Appending a consistent industry code to your CRM accounts lets you report win rates and pipeline by industry using one classification system, and compare your results with public statistics.
U.S. government economic data is published by NAICS industry, including the Census Bureau’s County Business Patterns. Reviewing how many establishments exist in an industry and region helps you decide how large a list is realistic before you spend.
Look up the primary industry code for your best accounts and note the patterns. If most of your top customers share a four-digit group, that group is your first candidate. Our guide to a B2B prospect list shows how to build the customer profile behind the codes.
Search the Census Bureau’s NAICS site by keyword or code, and use OSHA’s SIC search for the 1987 manual. Read the full definition, including what a code includes and excludes, instead of relying on the title alone.
| Level | Example | Best for | Risk |
|---|---|---|---|
| 2-digit sector | 23: Construction | Broad market sizing | Too broad to describe a buyer |
| 3 or 4 digits | 2382: Building Equipment Contractors | Testing adjacent industries | May include trades that do not need your product |
| 5 or 6 digits | 238220: Plumbing, Heating, and Air-Conditioning Contractors | Precise targeting | May be too narrow and miss businesses classified nearby |
A practical approach is to start with the six-digit codes that match your best customers, then test neighboring codes as separate segments so you can see which ones perform.
Read the definitions around your core codes. Some activities are classified in nearby industries, and some companies list a secondary activity. Decide which neighbors to include, test or exclude.
Ask your provider which classification its records carry and whether it stores primary and secondary codes. If records carry SIC, you may need to convert your NAICS selections with a correspondence table. If they carry both, you can cross-check your selection. Some commercial databases also extend SIC beyond four digits for more detailed targeting, so confirm what a provider’s codes represent.
Add employee and revenue bands, location and job titles so that the list describes a specific buyer. For geography, our guide to a mailing list by ZIP code explains how location filters work.
Request a sample that includes the industry code fields. Check whether the sampled companies really belong in the industry you intended, and estimate what share of the sample is a good fit. Adjust your codes before you buy the full list.
Access CampaignLake's Industry-Specific Email Database
Suppose a company sells scheduling and dispatch software for heating and cooling contractors. This hypothetical example illustrates the process.
| Segment | Codes | Additional filters | Roles |
|---|---|---|---|
| Core | NAICS 238220 (SIC 1711) | 10 to 99 employees, states where the company can support customers | Owners, general managers, service and operations managers |
| Adjacent test | NAICS 238210, Electrical Contractors and Other Wiring Installation Contractors | Same size and states, tested separately | Owners, general managers, operations managers |
The team first selects the core code and tests a neighboring code as its own segment. It adds size and geography, requests a sample with the code fields included, and checks that the sampled companies are contractors rather than equipment suppliers or manufacturers. It then sends a controlled campaign to each segment and compares replies and qualified meetings before widening or narrowing the codes.
To limit the risk, review sample records, use several related codes instead of one, and combine codes with other filters such as size, location and job title.
NAICS is revised every five years. On July 13, 2026, OMB published the Economic Classification Policy Committee’s proposed updates for 2027 for public comment. If adopted, the revision would apply to establishment data for periods beginning on or after January 1, 2027. The proposal is limited in scope: it clarifies definitions, recognizes some new industries and combines some existing ones. OMB has said it will publish the final changes in the Federal Register, so check the Census Bureau NAICS site for the final version.
Examples from the proposal include:
The proposed changes concentrate on manufacturing and a handful of other industries. The proposal’s change tables do not list codes such as 621111, 238220 or 541511 used in this guide. Even so, ask providers which NAICS version their codes follow and how they plan to handle the update, and keep a record of the codes you selected so you can review them when the final list is released.
Targeting by industry code does not change a sender’s obligations. The FTC’s CAN-SPAM guidance states that the law has no exception for business email, so commercial messages need accurate sender information, a valid postal address and a working opt-out that you honor within 10 business days. Rules outside the United States differ, so confirm the requirements for each market.
Before buying a code-based list, ask the provider:
CampaignLake provides B2B contact data that can be segmented by industry, including SIC and NAICS codes, together with job title, seniority, company size, revenue and geography, delivered as CSV or Excel files. Tell the team which codes or industries you want to reach and request a free sample so you can review the records before you buy.
Browse CampaignLake’s industry email lists, including manufacturing, construction, the IT industry, healthcare and real estate, or explore the broader B2B email list page. For a custom code-based list, contact CampaignLake.
A SIC code is a four-digit Standard Industrial Classification code that identifies a business’s primary industry. The system is based on the 1987 manual, which NAICS replaced as the federal statistical standard in 1997, but SIC codes are still used in SEC EDGAR filings and many business databases.
A NAICS code is a code of up to six digits in the North American Industry Classification System, the standard used by U.S. federal statistical agencies to classify business establishments. Each digit narrows the classification from sector to national industry.
SIC uses four digits and the 1987 structure, while NAICS uses up to six digits, is shared by the U.S., Canada and Mexico, and is revised every five years. The two do not map one to one, so use correspondence tables and check samples when converting between them.
Yes, although not as the federal statistical standard. OSHA hosts the 1987 SIC manual, SEC EDGAR filings carry SIC codes, and many commercial databases and CRMs still store SIC codes alongside or instead of NAICS.
Search the Census Bureau’s NAICS site by keyword or code and read the full definition. You can also check how your best customers are classified in your CRM or in a business database.
Many providers offer industry targeting by NAICS or SIC code. CampaignLake lists SIC and NAICS code among its targeting filters, and you can request a free sample by sharing your target codes or industries, job titles and location.
Use the system your provider’s records carry, and ask whether both are available. NAICS is the current standard and more detailed, while SIC remains common in legacy data. If both are available, use one to cross-check the other.
No. A code identifies the industry of the company. To reach the right person, add job title, seniority or department filters.
Yes. Because codes describe primary activity, and NAICS classifies establishments, a company or its locations can carry different codes. Ask whether your provider includes primary and secondary codes.
OMB published proposed updates in the Federal Register on July 13, 2026. They combine some manufacturing and other industries and change a few titles, and they would apply to establishment data for periods beginning on or after January 1, 2027. Check the Census Bureau NAICS site for the final version.
It varies by provider and source. Codes can be assigned by different methods, and companies can change what they do. Review a sample, ask how codes are assigned and verified, and test related codes instead of relying on a single one.
Use six-digit codes for precise targeting and two- to four-digit codes for market sizing or to test neighboring industries. Very broad codes make it harder to write relevant messages, while very narrow ones can miss prospects.
SIC and NAICS codes give B2B marketers a shared, standardized way to define industries. NAICS is the current standard and SIC remains widespread in legacy data, so the practical skill is knowing which your data carries and how to translate between them.
Choose codes from your best customers, read the official definitions, test adjacent codes separately, and add size, geography and role filters. Check a sample before you buy, and stay alert to the NAICS 2027 update. Used this way, industry codes make a list more precise without pretending to be more than a classification.
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Tanoj Kumar writes the CampaignLake blog's guides on B2B data, industry and professional email lists, and B2B lead generation.
