UDI labeling compliance

The UDI must appear on the label in both human-readable and machine-readable form, in the right format, and it must agree with what you registered. Most defects we find are in the gap between those three.

What a compliant UDI carrier looks like

A UDI has two halves. The Device Identifier (DI) is fixed and identifies the specific version or model and its labeler. The Production Identifiers (PI) are variable — lot or batch, serial number, expiration date, and production date, depending on what your device requires.

In GS1 format these are carried by Application Identifiers:

AI	Meaning	Format notes
(01)	GTIN / Device Identifier	14 digits, ends in a mod-10 check digit
(10)	Lot or batch	Up to 20 characters
(11)	Production date	YYMMDD
(17)	Expiration date	YYMMDD, day 00 means end of month
(21)	Serial number	Up to 20 characters

The defects we find most often

• Date format errors. Dates printed as MMDDYY, or with slashes and hyphens. GS1 date AIs are YYMMDD, full stop. Scanners and registries reject anything else.
• Human-readable and AIDC disagreeing. The printed LOT says one thing, the encoded (10) says another. Both must match exactly.
• Failing check digits. A GTIN-14 whose final digit does not reconcile against the mod-10 calculation. This one is trivially preventable and still common.
• Missing production identifiers where the device class requires them — or, just as costly, PI printed on devices that are exempt.
• Print quality below grade. A symbol that scans on your bench can still fail a hospital's scanner. Grading to ISO/IEC standards is not optional in practice.

You can check a UDI string yourself with our free UDI decoder, which parses GS1 Application Identifiers and validates GTIN check digits in your browser.

Direct marking

Devices intended to be reprocessed and reused must bear a UDI as a direct marking on the device itself — etched, engraved, or applied via AIDC — in addition to the label. Exceptions apply where marking would interfere with safety or performance, or where it is not technologically feasible, but those exceptions need documenting rather than assuming.

The US deadline for reusable Class I direct marking was December 2022. Australia's direct marking obligations run through 2029.

Printer qualification and design controls

If you print labels in house, the printer is part of your compliance system. We remotely perform IQ/OQ/PQ for in-house printers so output meets and exceeds print quality and scanning verification requirements per 21 CFR Part 11. We also execute identification and approval of User Needs, Design Inputs, Trace Matrix, and Design Transfer as part of design controls.

Highly individualized devices

Contact lenses, spectacle lenses, frames, and ready-to-wear reading spectacles would generate an unmanageable number of individual UDI-DIs under a naive scheme. The Master UDI-DI approach groups devices sharing relevant design and manufacturing characteristics instead. Our team helped develop this solution through GS1 working groups, and MDCG 2025-8 provides the current guidance.

What triggers a new DI

A new Device Identifier is required whenever a change creates a new version or model:

1. A new size or dimension offered to the market
2. A change in labeled quantity — the 10-pack and the 25-pack are different
3. A change in sterility
4. Clinically relevant specification changes
5. A new brand name or model designation

Cosmetic label updates usually do not. The failure mode is not deciding wrong once — it is having no process that asks the question before the change ships.