UDI and Basic UDI-DI

Updated July 2026

The UDI system, or Unique Device Identification, is the unique device identification system provided for by Regulation (EU) 2017/745.

This guide explains, for informational purposes, what UDI, UDI-DI, UDI-PI and Basic UDI-DI are in the MDR context, what role they play in the identification and traceability of medical devices, and why the Basic UDI-DI should not be confused with the UDI placed on the label or packaging.

Sheet with the title UDI and Basic UDI-DI Regulation (EU) 2017/745

In this guide

What are UDI and Basic UDI-DI under the MDR?

The MDR provides for a unique device identification system, called the UDI system, intended to enable the identification and facilitate the traceability of medical devices.

In general terms, the UDI system applies to devices other than custom-made devices and investigational devices.

The UDI is a numeric or alphanumeric code created on the basis of internationally accepted device identification and coding standards. It consists of elements that make it possible to identify the device and, where applicable, certain information relating to production.

The Basic UDI-DI, by contrast, has a different function. It is not the code that identifies an individual production unit or a specific packaging level. It is the primary identifier of a device model and links devices with the same intended purpose, the same risk class and common essential design and manufacturing characteristics.

This distinction is important because UDI and Basic UDI-DI are often confused, even though they perform different functions within the MDR system.

What is the UDI system used for?

The UDI system is intended to improve the identification of medical devices and facilitate their traceability along the supply chain and during use.

In general terms, the UDI system makes it possible to link a device to information recorded in the UDI database and may support several activities provided for by the MDR, including device registration, market surveillance, vigilance and the management of information relating to the device.

The UDI may also be used in the context of reporting serious incidents and field safety corrective actions.

It is important to remember that placing the UDI is an additional requirement. It does not replace the other marking or labelling requirements provided for by the MDR.

UDI, UDI-DI and UDI-PI

The UDI consists of two main elements:

UDI = UDI-DI + UDI-PI

The UDI-DI, or Unique Device Identifier – Device Identifier, is the part of the UDI that identifies the device model. It is a unique numeric or alphanumeric code specific to a device model and is also used as an access key to the information stored in the UDI database.

The UDI-PI, or Unique Device Identifier – Production Identifier, identifies the device production unit.

Depending on the case, the UDI-PI may include elements such as the lot number, serial number, software identification, date of manufacture or expiry date.

In general terms, the UDI-DI relates to the identification of the device model, while the UDI-PI relates to production information associated with that device.

The term “unique” does not necessarily mean that each individual production unit must be serialised. The UDI enables the unambiguous identification of the device on the market according to the structure provided for by the UDI system and the applicable rules.

What is the Basic UDI-DI?

The Basic UDI-DI, or basic UDI-DI, is the primary identifier of a device model. The Basic UDI-DI links devices with the same intended purpose, the same risk class and common essential design and manufacturing characteristics.

Unlike the UDI, the Basic UDI-DI is not intended to appear as a UDI carrier on the label or packaging of the device. It does not identify an individual production unit, a lot, a serial number or a specific packaging level.

Under the MDR, the Basic UDI-DI has a regulatory and documentary function. It is the main key information for certain registrations in the UDI database and is referred to in documents such as the EU declaration of conformity and, where relevant, certificates issued by the notified body.

The Basic UDI-DI can therefore be seen as a regulatory reference for the device model, while the UDI placed on the label or packaging serves the identification and traceability of the device on the market.

Difference between UDI-DI and Basic UDI-DI

The difference between UDI-DI and Basic UDI-DI is one of the most important aspects of the UDI system.

The UDI-DI is part of the UDI. It is linked to the device and its packaging levels and allows access to the information recorded in the UDI database.

The Basic UDI-DI, by contrast, is not part of the UDI placed on the label or packaging. It is a regulatory identifier used to link a device model or group of devices to information, documents and registrations provided for by the MDR.

In simple terms:

  • UDI-DI = identifier of the device model within the UDI
  • UDI-PI = production identifier
  • Basic UDI-DI = main regulatory identifier of the device model or group of devices

This distinction is also relevant because the Basic UDI-DI appears in certain regulatory documents, while the UDI carrier concerns the label, the device or the packaging, according to the conditions provided for by the MDR.

Confusing UDI-DI and Basic UDI-DI may lead to errors in reading regulatory documentation, registering devices or understanding the information connected to the UDI database.

Where does the Basic UDI-DI appear?

The Basic UDI-DI is referred to in several parts of the MDR and may appear in various regulatory documents or processes.

In general terms, the Basic UDI-DI may be present:

  • in the EU declaration of conformity;
  • in the technical documentation;
  • in the information provided to the UDI database;
  • in the device registration;
  • in certificates issued by the notified body, where applicable;
  • in the conformity assessment process, in cases where the involvement of a notified body is required;
  • in the summary of safety and clinical performance, or SSCP, where required.

The EU declaration of conformity includes the Basic UDI-DI. The technical documentation also contains information relating to the description and identification of the device, including the Basic UDI-DI when device identification is based on the UDI system.

For devices subject to certain conformity assessment procedures involving a notified body, the Basic UDI-DI may also play a role in the application and certification process.

UDI on the label and packaging

The UDI is presented through a UDI carrier.

The UDI carrier is the means of conveying the UDI using an automatically readable format and, where required, a human-readable form.

In the language of the MDR, reference is made to:

  • AIDC, meaning automatic identification and data capture;
  • HRI, meaning human-readable interpretation.

AIDC technologies may include, for example, linear barcodes, 2D/Matrix codes or RFID.

In general terms, the UDI carrier appears on the label of the device, on the device itself or on the external packaging levels, according to the conditions provided for by the MDR and Annex VI.

External packaging levels do not include shipping containers.

The UDI system may therefore involve both the device and the different packaging levels, but the applicable rules depend on the type of device, the packaging, the intended purpose and the conditions provided for by the Regulation.

UDI database and EUDAMED

The MDR provides for the establishment of a UDI database intended to collect, validate, process and make available certain basic information relating to devices.

The UDI database is connected to EUDAMED, the European database on medical devices.

In the MDR context, the manufacturer provides the UDI database with the UDI-DI and the basic data referred to in Annex VI, Part B.

The basic information may include, for example, the Basic UDI-DI, the manufacturer’s name and address, the device risk class, the device model or reference, storage or handling conditions where applicable, and the status of the device on the market.

The UDI database is not designed to contain UDI-PI or confidential commercial information on products.

From 28 May 2026, the EUDAMED UDI/Devices module is mandatory under the applicable transitional provisions, following the Commission’s declaration of functionality of the first modules.

The presence of information in the UDI database should not, by itself, be interpreted as evidence of the device’s conformity with the MDR. Conformity depends on compliance with the applicable requirements of the Regulation and the relevant documentation.

UDI, technical documentation and EU declaration of conformity

UDI system is also connected to the technical documentation and the EU declaration of conformity.

The manufacturer maintains an up-to-date list of all UDIs assigned as part of the technical documentation.

Technical documentation also contains information relating to the description and identification of the device, including the Basic UDI-DI when device identification is based on the UDI system.

The manufacturer’s quality management system also includes aspects connected to the UDI system, including verification of the assignment of UDIs to the relevant devices and consistency of the information provided as part of device registration.

For this reason, the UDI system should not be considered only as a graphic element to be placed on the label. It is connected to technical documentation, registration, the quality system and device traceability.

Recording and storing UDIs

The MDR also provides for obligations to record and store UDIs for certain subjects and categories of devices.

In general terms, economic operators record and store, preferably electronically, the UDIs of devices they have supplied or received when the conditions provided for by the Regulation are met.

Healthcare institutions record and store, preferably electronically, the UDIs of class III implantable devices they have supplied or received.

For devices other than class III implantable devices, Member States may encourage or require forms of recording and storing of UDIs by healthcare institutions and healthcare professionals.

The concrete scope of these obligations may therefore depend on the type of device, the subject involved and any applicable national provisions.

UDI and specific cases

Annex VI to the MDR provides specific rules for certain types of devices or situations.

These cases may include, for example:

  • implantable devices;
  • reusable devices requiring cleaning, disinfection, sterilisation or refurbishment between uses;
  • systems and procedure packs;
  • configurable devices;
  • software;
  • packaging levels;
  • changes that may require a new UDI-DI;
  • highly individualised devices for which the Master UDI-DI may be relevant.

For reusable devices requiring processes between uses, the MDR provides specific conditions for the presence of the UDI carrier on the device itself, except where direct marking would interfere with the safety or performance of the device or would not be technologically feasible.

For software, the UDI is assigned at the system level of the software in the cases provided for. Certain changes may require a new UDI-DI, while minor revisions may be managed through the UDI-PI, according to the logic described in Annex VI and the relevant MDCG guidance documents.

Systems, procedure packs and configurable devices also follow specific rules.

This guide does not report all specific rules, because the concrete application of the UDI system requires an assessment of the device, its configuration, packaging, software, changes made and the rules of the applicable issuing entity.

Master UDI-DI

The Master UDI-DI is a specific solution provided for certain categories of highly individualised devices.

In general terms, it may concern groups of devices that present specific similarities with respect to defined design parameters, as is the case for certain categories of ophthalmic devices.

Master UDI-DI should not be confused with the Basic UDI-DI.

The Basic UDI-DI is the main regulatory identifier of a device model or group of devices in the MDR system. The Master UDI-DI, by contrast, is a specific solution provided for certain highly individualised devices, according to the applicable conditions and rules.

Why this guide does not assign UDIs to devices

This guide does not assign UDI, UDI-DI, UDI-PI, Basic UDI-DI or Master UDI-DI to specific devices.

It also does not establish when a new UDI-DI must be assigned, how the coding rules of an issuing entity must be applied or which information must be managed in a specific case.

The assignment and management of identifiers depend on several elements and for this reason, this guide is descriptive in nature and refers to the MDR text, Annex VI and the relevant MDCG documents.

Informational note

This guide is published for informational purposes only and does not constitute regulatory, legal, technical or professional advice.

The information is based on publicly available sources and was verified as of the date of publication or the latest update of this page. It may therefore not reflect subsequent changes or developments.

For assessments relating to specific cases, reference should be made to the official texts, the latest documentation issued by the competent authorities and, where appropriate, qualified professionals.

Official sources

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© Simone Ronco. Unless otherwise stated, the editorial content of this guide is an original work.

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