CAS Registry Number Search, Verification and Application Support

CAS Registry Number Services at a Glance

What Is a CAS Registry Number?

A CAS Registry Number is a numeric identifier assigned to a specific substance within CAS REGISTRY. Since chemical substances may be described by molecular formulas, structures, systematic names, common names, trade names, or internal codes, CAS RNs help provide a consistent way to identify substances across different databases, languages, regulatory systems, and supply chains.

A CAS RN can contain up to 10 digits and is divided by hyphens into three parts:

• The first part: up to 7 digits;

• The second part: 2 digits;

• The third part: 1 check digit.

The check digit is used to verify the validity and uniqueness of the CAS RN. For example, the CAS number for water is 7732-18-5, where "5" is the check digit.

CAS states that CAS RNs are unique and internationally recognized identifiers for specific substances, and that governmental agencies rely on them for substance identification in regulatory applications because they are unique, easily validated, and internationally recognized.

Why CAS Numbers Matter for Chemical Compliance

In chemical compliance projects, substance identity must be accurate before a company can determine inventory status, registration obligations, SDS disclosure, hazard classification, customs classification, or market access requirements.

A correct CAS RN can help companies:

• Confirm whether the same substance is being discussed across suppliers, customers, databases, and regulators;

• Reduce confusion caused by inconsistent names, synonyms, trade names, or internal product codes;

• Support chemical inventory status checks;

• Prepare SDSs, labels, technical documents, and regulatory dossiers;

• Support customs declarations and import/export documentation;

• Facilitate chemical registration programs such as EU REACH, China New Chemical Substance Registration, U.S. TSCA compliance, K-REACH, and Japan CSCL/ISHL;

• Improve internal chemical data management and international supply chain communication.

However, companies should not rely on a CAS RN alone. Substance identity should also be reviewed based on composition, structure, manufacturing process, impurities, analytical data, and intended regulatory use.

Who Needs This Service?

You may need CAS number search, verification, or application support if your company is:

• Developing or commercializing a new chemical substance;

• Handling a proprietary, patented, or pre-commercial substance;

• Preparing a chemical regulatory submission in the EU, U.S., China, Korea, Japan, or other markets;

• Reviewing whether a substance is already listed on a chemical inventory;

• Preparing SDSs, labels, customs documents, or technical dossiers;

• Handling polymers, UVCBs, reaction products, extracts, enzymes, proteins, or other complex substances;

• Receiving inconsistent CAS numbers from suppliers, customers, or third-party databases;

• Needing a CA Index Name for regulatory, R&D, patent, internal database, or compliance documentation purposes;

• Unsure whether a commercial material should be assessed as one substance or by its individual components.

What Types of Substances May Be Covered?

CAS REGISTRY covers a wide range of substances, including organic and inorganic compounds, metals and alloys, minerals, coordination compounds, organometallics, elements, isotopes, proteins, nucleic acids, polymers, and UVCBs.

For service assessment purposes, substances may include the following categories:

Formulated commercial mixtures or trade products usually cannot be represented by one CAS RN unless the material can be defined as a distinct registrable substance. Some complex substances, such as polymers, UVCBs, reaction products, extracts, or industrial process products, require case-by-case substance identity assessment before selecting the appropriate CAS service route.

Substances that are generally not suitable for CAS RN assignment may include broad substance categories, undefined trade products, finished commercial formulations, living organisms, or insufficiently described materials.

Information Required for CAS RN Search or Application

To support accurate CAS RN search, verification, or application, companies should prepare as much substance identity information as possible. Incomplete or inconsistent information may lead to delays, supplementary requests, mismatched results, or an incorrect service route.

Additional information may include:

• Existing CAS numbers or names provided by suppliers;

• Trade names, synonyms, or internal codes;

• Intended regulatory use of the CAS RN or CA Index Name;

• Target market or regulatory framework;

• Confidentiality requirements, if any.

CAS Service Routes

Different business scenarios may require different CAS service routes. REACH24H can help assess the appropriate route based on substance identity, available information, regulatory purpose, and confidentiality requirements.

For common and frequently regulated chemicals, CAS Common Chemistry may be used as an initial search resource. CAS states that CAS Common Chemistry provides access to nearly 500,000 chemical substances from CAS REGISTRY.

For new, proprietary, complex, or regulatory-sensitive substances, companies should conduct a more structured identity review before selecting the service route.

REACH24H Service Process

Step 1: Substance Identity Scoping

REACH24H reviews the available substance information, including substance name, structure, composition, manufacturing process, source, analytical data, existing CAS numbers, and intended regulatory use.

Step 2: Data Gap Review

We assess whether the available information is sufficient for CAS RN search, CAS number verification, CA Index Name confirmation, or CAS RN application support. If data gaps are identified, we provide recommendations on supplementary information.

Step 3: Service Route Assessment

Based on the substance identity and business objective, REACH24H helps determine the appropriate route, such as CAS Registry Lookup, Chemist Consultation, Inventory Expert Service, CA Index Name confirmation, or CAS RN application support.

Step 4: Document Preparation

REACH24H supports the organization and preparation of required technical information, including structural, compositional, process-related, source-related, and analytical details.

Step 5: Communication and Follow-up Support

We support communication and follow-up with CAS Registry Services, including clarification of supplementary information where needed.

Step 6: Result Review and Regulatory Use

After the result is received, REACH24H helps review the CAS RN and/or CA Index Name and supports its proper use in SDSs, registrations, chemical inventory checks, customs documents, and other compliance projects.

Step 7: Downstream Compliance Alignment

Where needed, REACH24H can further support the alignment of CAS results with EU REACH, U.S. TSCA, China New Chemical Substance Registration, K-REACH, Japan CSCL/ISHL, GHS/SDS, and other global chemical compliance requirements.

Timeline and Cost Factors

The timeline and cost of a CAS RN project depend on the selected service route and the complexity of the substance. The timeline should not be assessed based on the CAS number alone.

Key factors include:

• Whether the substance is already present in CAS REGISTRY;

• Whether the request involves lookup, verification, CA Index Name confirmation, Chemist Consultation, Inventory Expert Service, or CAS RN application support;

• Substance complexity, such as polymer, UVCB, extract, enzyme, reaction product, or industrial process product;

• Completeness and consistency of the technical information;

• Whether supplementary information is requested;

• Whether confidentiality concerns need to be assessed before submission;

• The intended regulatory use and urgency of the project;

• Whether downstream compliance review is required after the CAS result is obtained.

For known-substance lookup cases, CAS indicates that results may be returned within 24 hours, excluding weekends and holidays, if the submitted chemical name or CAS RN matches a CAS REGISTRY record. More complex cases may require additional review and technical clarification.

Confidentiality and Publication Considerations

Confidentiality should be considered before starting a CAS RN project, especially for novel, proprietary, patented, or pre-commercial substances.

A CAS RN assignment may involve the addition of substance information to CAS REGISTRY. If confidentiality is required, companies should assess whether CAS RN application is appropriate or whether CA Index Name confirmation or another approach may be more suitable.

Companies should also consider how CAS results will be used in public documents, regulatory submissions, SDSs, product databases, commercial platforms, or supplier communication. CAS notes that licensing may be required when an organization publishes CAS Registry Numbers to the public or uses them to support features of a publicly or commercially available platform.

REACH24H can help review confidentiality concerns, clarify the intended regulatory use, and support companies in selecting a suitable service route before submission.

How REACH24H Can Help

REACH24H provides practical CAS number support as part of global chemical regulatory compliance projects.

Our services include:

• CAS RN search and verification;

• CAS RN application support for new or complex substances;

• CA Index Name confirmation support;

• Substance identity review and technical data gap analysis;

• Preparation and organization of required chemical identity information;

• Review of supplier-provided CAS numbers and substance names;

• Support for polymers, UVCBs, reaction products, extracts, industrial process products, and biotechnological substances;

• Communication and follow-up support with CAS Registry Services;

• Review of CAS results and their regulatory implications;

• Alignment of CAS results with SDSs, chemical inventory checks, customs documents, and registration dossiers;

• Regulatory pathway assessment for EU REACH, U.S. TSCA, China New Chemical Substance Registration, K-REACH, Japan CSCL/ISHL, and other chemical compliance frameworks.

Frequently Asked Questions (FAQ)

Official References and Data Resources

• CAS REGISTRY - official CAS substance information resource.

• CAS Registry Services - official CAS service information for CAS RNs and CA Index Names.

• CAS Registry Lookup - official lookup service for matching CAS RNs or CA Index Names.

• CAS Common Chemistry - public CAS chemical substance search resource.

• ECHA Information on Chemicals - EU chemical information and inventory-related reference.

• U.S. EPA TSCA Chemical Substance Inventory - U.S. chemical inventory reference.

• PubChem - authoritative chemical information resource maintained by the U.S. National Library of Medicine.

• NIST Chemistry WebBook - chemical and physical property data resource.

Recommended Reading

• EU REACH Registration and Compliance Services

• China New Chemical Substance Registration

• U.S. TSCA Compliance Support

• K-REACH Registration and Compliance Services

• Vietnam Chemical Registration and Compliance