The UDI (Unique Device Identification) is the unique identification system mandated by Article 27 of the MDR. Its purpose: to ensure the traceability of every medical device from manufacture to patient, and to feed the EUDAMED database with reliable data on products placed on the market.
The structure of a UDI
A UDI is made up of two distinct parts, which serve different purposes. The UDI-DI (Device Identifier) identifies the model or commercial reference of the device. It is specific to each version and to each level of packaging. A significant change to the device (new version, new packaging, change of sterilisation process) requires a new UDI-DI; the list of cases is set out in Annex VI, Part C of the regulation. The UDI-PI (Production Identifier) identifies the production unit: lot number, serial number, manufacturing date, expiry date. It changes with each lot or unit manufactured. The complete UDI applied to the label combines UDI-DI and UDI-PI.
The Basic UDI-DI, the identifier no one sees but everyone requires
The system’s third identifier, and the first point of confusion in SMEs: the Basic UDI-DI. It never appears on the label. It groups together devices that share the same intended purpose, the same risk class and the same essential design and manufacturing characteristics. Yet it is what structures everything else. The Basic UDI-DI is the main access key for EUDAMED registrations. It appears on the EU declaration of conformity and on the certificates issued by the notified body. The MDCG 2018-1 guide sets out its allocation rules. The classic mistake is to confuse it with the UDI-DI and to multiply Basic UDI-DIs reference by reference. The result: an unmanageable EUDAMED tree structure and certificates to be revised at the first grouping. The grouping logic is decided before the first allocation, not after.
The issuing entities
The manufacturer does not allocate its own UDI codes. It goes through an issuing entity designated by the European Commission (Implementing Decision (EU) 2019/939, designations renewed until 27 June 2029 by Decision (EU) 2024/2120). Four entities are designated: GS1: uses the GTIN format. It is the most widely used entity in the medical device sector in Europe. Membership provides access to a GS1 Company Prefix, from which the manufacturer builds its product codes. HIBCC: HIBC format, more common in North America. ICCBBA: ISBT 128 format, used mainly for products of human origin and cell therapies. IFA GmbH: German entity, PPN format, originating from the pharmaceutical channel. Relevant for manufacturers whose products already circulate in the German pharmaceutical distribution chain.
The accepted marking formats
The UDI must appear on the label in a human-readable format (HRI) and in a machine-readable format (AIDC). The GS1 Data Matrix is the sector’s most common format. For reusable devices reprocessed between two uses (cleaning, disinfection, sterilisation), direct marking on the device itself is an obligation, not an option, unless a documented technical impossibility applies. This obligation follows its own timetable, offset by two years from the label: May 2023 for class III and implantables, May 2025 for classes IIa and IIb, May 2027 for class I.
The application deadlines by class
The application of the UDI on the label has been in effect since May 2021 for class III and implantables, May 2023 for classes IIa and IIb, May 2025 for class I (Article 123 of the MDR). Registration in EUDAMED follows a separate timetable. Since 28 May 2026, the use of the first four modules is mandatory, including the UDI/devices module. In concrete terms: across all classes, a manufacturer placing a device on the market must now have registered its Basic UDI-DIs and UDI-DIs in the database. The period when registration was voluntary is over. Manufacturers still under directive certificates under the transitional regime of Article 120 must check their situation on a case-by-case basis: “legacy” devices follow specific registration arrangements, with their own EUDAMED identifiers. For manufacturers established outside the Union, these registration obligations for non-EU manufacturers rest in part on the authorised representative, who verifies that the devices it represents are indeed registered.
What this means in practice
UDI implementation follows a sequence in which each step conditions the next: choose an issuing entity, obtain a prefix, decide the grouping logic for Basic UDI-DIs, allocate UDI-DIs reference by reference, integrate UDI-PIs into the manufacturing and labelling processes, register everything in EUDAMED, then formalise a UDI management procedure in the QMS for future changes. The bottleneck is almost never the code itself. It is the grouping decision taken too quickly, upstream, without anticipating the product variants of the next three years. A class I manufacturer with forty references and reusable devices has two projects ahead: an already-due EUDAMED registration, and direct marking to organise before May 2027. Engraving a Data Matrix on an existing instrument affects the manufacturing process, sometimes the technical documentation. Twelve months of industrial lead time is nothing exceptional. Having someone structure your UDI system and EUDAMED registration today costs a documentary review. Letting it surface when an assessor comes to audit your ISO 13485 QMS costs a non-conformity. This traceability does not only serve registration: in the event of an incident, it also conditions compliance with the serious-incident reporting deadlines.
Regulatory source: Article 27 and Annex VI of Regulation (EU) 2017/745 — EUR-Lex. Implementing Decisions (EU) 2019/939 and (EU) 2024/2120. MDCG 2018-1 guide.