GLN Structure Explained: How the 13-Digit Identifier Powers DSCSA Compliance and EPCIS Traceability

A Global Location Number (GLN) is more than just a random identifier - it is a precise, standardized code that tells trading partners exactly which business, location, or functional area within a business is involved in a serialized drug transaction. Understanding how GLNs are structured is essential for accurate EPCIS data exchange and maintaining Drug Supply Chain Security Act (DSCSA) compliance across the supply chain.

Below is a component-level breakdown of how a GLN is constructed and the significance of each element.

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Breakdown of the 13-Digit GLN Format

A GLN consists of 13 digits, structured to ensure uniqueness, global compatibility, and machine readability.
The general format is:

[Company Prefix][Location Reference][Check Digit]

Each part supports Electronic Product Code Information Services (EPCIS) interoperability and helps trading partners maintain accurate transaction records.

1. GS1 Company Prefix

The company prefix is a unique identifier assigned by GS1 to an organization. It ensures that all GLNs, GTINs, SSCCs, and EPCIS-related identifiers generated by that company are globally unique.

Key points:

• Purchased from GS1

• Used across multiple GS1 identifiers

• Forms the foundation for creating valid GLNs

For pharmacies and distributors, the company prefix enables them to generate GLNs for stores, departments, distribution centers, or any serialized activity linked to DSCSA requirements.

2. Location Reference

The location reference defines the specific location within the company.

This allows a business to assign unique GLNs to:

• Pharmacy sites

• Distribution centers

• Receiving docks

• Corporate offices

• Technology systems

• Functional departments

Accurate location references help ensure EPCIS data aligns with the movement of product — a key aspect of effective DSCSA compliance.

3. Check Digit

The final digit of a GLN is the check digit, calculated using a GS1 algorithm to ensure the identifier is valid.

It helps detect:

• Data entry errors

• Scanning errors

• Invalid GLN structures

Because GLNs appear throughout serialized event data, the check digit plays a crucial role in preventing EPCIS mismatches and improving DSCSA traceability.

How GLNs Differ from GTINs

Although GLNs and GTINs share GS1 foundations, they serve very different functions:

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In EPCIS events:

• GTIN = the serialized product

• GLN = the responsible location or entity

Both are required for clean interoperability under DSCSA.

GLNs for Legal vs. Physical Locations

GLNs can represent different types of locations, and using the correct one is essential for accurate EPCIS reporting.

Legal Entity GLNs

Identify the business entity involved.

Used for ownership, licensing, and trading partner identity.

Location GLNs

Identify the actual place where a serialized action occurs, such as:

• A pharmacy

• A warehouse

• A shipping dock

• A receiving station

• A technology system

Under DSCSA, EPCIS files often include both a legal entity GLN and a location GLN, depending on the event type.

Summary

GLNs are a foundational element of DSCSA compliance, enabling supply chain partners to uniquely identify every business and physical location involved in serialized drug transactions. By understanding the structure of the 13-digit GLN — including the company prefix, location reference, and check digit — pharmacies and trading partners can ensure accurate EPCIS data, prevent mismatches, and maintain complete traceability.

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Want to learn more about GLNs? Explore the related articles in our blog series to dive deeper into how GLNs work, why they matter, and how they’re used across the supply chain.

• Introduction to GLNs: The Foundation of Global Track-and-Trace, DSCSA Compliance, and EPCIS Data Exchange
• How GLNs Are Used in DSCSA & EPCIS: Why Every Pharmacy Needs Accurate Location Data

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