UDI under the MDR and IVDR: UDI-DI, UDI-PI, Issuing Entities, Carriers and the Deadlines by Class

Custom-made and investigational devices under the MDR, and devices for performance studies under the IVDR, are outside the UDI system, and MDCG 2021-25 rev.1 explains that MDR Article 27 does not apply to legacy devices.

The UDI concerns everyone who handles a device. The manufacturer assigns the UDI and is the only party that places it on the device or its packaging. Economic operators and health institutions store the UDI of class III implantable devices; for economic operators further devices follow by implementing act, and member states may require health institutions to store UDIs of other devices (MDR Article 27(8) and (9)).

This page explains the two parts of a UDI and when a change needs a new UDI-DI. It then covers who assigns UDIs under which designation decisions, how the UDI appears on the label, the label and direct-marking dates by class, the UDI database, the storage duties and the MDCG guidance documents with their revisions.

What UDI Means under the MDR and IVDR

MDR Article 2(15) defines the Unique Device Identifier as a series of numeric or alphanumeric characters, created through internationally accepted device identification and coding standards, that allows unambiguous identification of specific devices on the market. The definition rests on two elements: the code follows internationally accepted coding standards, and it identifies one specific device without ambiguity. The identification serves traceability: MDR Article 33(1)(b) names the unique identification of devices and their traceability among the purposes of EUDAMED, the database that hosts the UDI data.

The UDI system covers devices under both EU medical device regulations, the MDR (Regulation (EU) 2017/745) and the IVDR (Regulation (EU) 2017/746). Both regulations entered into force on 25 May 2017; the MDR has applied since 26 May 2021 and the IVDR since 26 May 2022, and both are directly applicable in every member state without national transposition. How UDI fits into the framework of the EU MDR and IVDR is explained on the home page.

UDI stands for Unique Device Identifier, and in medical terms it is an identifier: it is not a device class or a certificate. The identifier is made of two parts, a device identifier and a production identifier, which the section on the two parts below explains one by one.

The Legal Basis: MDR Articles 27 and 28, IVDR Articles 24 and 25, and Annex VI

MDR Article 27 sets up the UDI system and MDR Article 28 the UDI database; IVDR Articles 24 and 25 do the same for in vitro diagnostic devices, and Annex VI of each regulation holds the detailed rules. The text of the articles is available in the consolidated MDR on EUR-Lex and the consolidated IVDR on EUR-Lex. Device registration, which uses the Basic UDI-DI as its key, follows in MDR Article 29 and IVDR Article 26.

Annex VI divides the UDI rules into parts. Part B lists the UDI core data elements that are provided to the UDI database together with the UDI-DI. Part C describes the UDI system itself: its definitions, the general requirements, the assignment of the UDI and the placement of the UDI carrier.

The UDI also reaches into the manufacturer's quality management system. MDR Article 10(9)(h) requires the quality management system to cover the verification of the UDI assignments made under MDR Article 27(3) and the consistency of the information provided under MDR Article 29, and IVDR Article 10(8)(h) sets the same aspect with references to IVDR Articles 24(3) and 26. MDCG 2021-19 (July 2021) is the MDCG guidance note on integrating the UDI within an organisation's quality management system. The UDI articles sit in Chapter III, on identification and traceability of devices, of the EU MDR (Regulation (EU) 2017/745).

Devices Outside the UDI System

The UDI system of MDR Article 27(1) does not apply to custom-made devices and investigational devices. The exclusion sits in the first paragraph of the article, so neither group needs a UDI-DI, a UDI-PI or a UDI carrier under the MDR.

Under IVDR Article 24(1), devices for performance studies are excluded from the UDI system of the IVDR. The last row of the dates table further down this page records the exclusions of both regulations side by side, next to the classes that carry the UDI.

Legacy devices are a third group. MDCG 2021-25 rev.1 (October 2024) explains that MDR Article 27 does not apply to legacy devices placed on the market under MDR Article 120(3). The performance-study rules and the other provisions for in vitro diagnostic devices are set out in the IVDR (Regulation (EU) 2017/746).

The Two Parts of a UDI: Device Identifier and Production Identifier

Every UDI has two parts under MDR Article 27(1)(a): a device identifier (UDI-DI) specific to a model of device, and a production identifier (UDI-PI) that identifies the unit of device production. IVDR Article 24 establishes the UDI system for in vitro diagnostic devices. The "UDI code" on a label is the two parts read together: the UDI-DI stays the same for every unit of a model at one packaging level, while the UDI-PI changes with the serial number, the lot or the date of the unit. A UDI-DI alone identifies a model at one packaging level; only the UDI-DI and the UDI-PI together identify a single unit or lot of that model. The syntax of the code depends on the issuing entity and belongs to the carriers page listed below. The table compares the two parts.

UDI-DI: One Code per Model and Packaging Level

The UDI-DI is a unique numeric or alphanumeric code specific to a model of device, and it is also the access key to the information stored in the UDI database (MDR Annex VI Part C Section 1). A device identifier therefore answers the question "which model is this?", and the database record behind it answers the follow-up questions about that model.

A UDI-DI is unique at each level of device packaging (MDR Annex VI Part C Section 3.4). A single unit, a box of units and a case of boxes each carry their own UDI-DI, even when the device inside is the same. The packaging level is therefore part of what a UDI-DI identifies: two scans of the same model at two packaging levels return two different device identifiers.

Each UDI-DI is associated with one and only one Basic UDI-DI, as MDCG 2018-1 rev.4 (April 2021) explains. The Basic UDI-DI is the primary identifier of a device model under MDR Annex VI Part C Section 1: a device identifier assigned at the level of the device unit of use, the main key for records in the UDI database, and the reference used in certificates and in the EU declaration of conformity, where it is point 3 of the content listed in MDR Annex IV. Certificates of free sale set out the Basic UDI-DI as provided to the UDI database as well (MDR Article 60(1), IVDR Article 55(1)). The Basic UDI-DI sits above the UDI-DIs of the model's packaging levels.

UDI-PI: Serial Number, Lot, Software Identification and Dates

The UDI-PI identifies the unit of device production and can be a serial number, a lot number, a software identification or a manufacturing date and/or expiry date (MDR Annex VI Part C Section 1). Where the only date on the label is the manufacturing date, that date is used as the UDI-PI (MDR Annex VI Part C Section 3.5). The UDI-PI is the variable part of the UDI: it tells one production unit or batch of a model apart from the next. For software, the software identification serves as the UDI-PI, which is why minor software revisions change the UDI-PI rather than the UDI-DI, as the section on new UDI-DIs shows. The UDI as a whole is also used for reporting serious incidents and field safety corrective actions under MDR Article 27(5).

Implantable devices follow stricter rules under MDR Annex VI Part C Section 6.1.2: active implantable devices carry a serial number, and other implantable devices a serial number or a lot number. UDI-PIs are never stored in the UDI database, because MDR Article 28(2) keeps them out of it. Lot and serial data therefore stay with the manufacturer and in the supply chain, where the storage duties described further down apply. For implants, the production data also reach the patient: the implant card of MDR Article 18(1)(a) carries the serial number, the lot number and the UDI of the device.

When a Change Needs a New UDI-DI

MDR Annex VI Part C Section 3.9 requires a new UDI-DI for a change of name or trade name, version or model, single-use labelling, sterile packaging, need for sterilisation before use, quantity in a package, or critical warnings or contra-indications such as latex or DEHP. A change of pack size from 10 to 20 units, for example, needs a new UDI-DI for the new pack. Changes that do not need a new UDI-DI are handled through the database update rule described further down.

MDCG 2018-1 rev.4 explains that a new UDI-DI is also needed for the changes listed below.

• Substances: the presence of CMR or endocrine-disrupting substances.
• Reuse: the maximum number of reuses, where the manufacturer claims one.
• Appearance: a change of colour or language, where it can lead to misidentification.

Software follows its own rule. Under MDR Annex VI Part C Section 6.5.3, minor software revisions, such as bug fixes, usability enhancements that are not for safety purposes, security patches and changes to operating efficiency, need a new UDI-PI, not a new UDI-DI. A software update therefore does not always need a new UDI-DI; the type of change decides. Relabelling has a rule of its own as well: a relabeller keeps a record of the original UDI under MDR Annex VI Part C Section 3.10, so the link to the manufacturer's identifier survives the new label. Which changes to a software as a medical device need a new UDI-DI is covered under software as a medical device under the MDR and IVDR.

UDI in Detail: The Model Identifier, Carriers and the Optics Solution

Three detailed pages cover what this overview summarises: the Basic UDI-DI that identifies a device model across packaging levels, the carriers that put the UDI on labels and devices, and the Master UDI-DI for highly individualised devices such as contact lenses and spectacles. This overview stays at the level of who assigns what and when. Identifier formats, check characters, carrier placement rules and the Master UDI-DI dates belong to the three pages in the table. The Master UDI-DI rests on two delegated regulations: Delegated Regulation (EU) 2023/2197 for contact lenses, which inserts Section 6.6 into MDR Annex VI Part C, and Delegated Regulation (EU) 2025/1920 for spectacle frames, spectacle lenses and ready-to-wear reading spectacles.

Issuing Entities and How UDIs Are Assigned

A manufacturer assigns UDIs under the rules of an issuing entity, an organisation the Commission designates under MDR Article 27(2) to operate a system for assigning UDIs, and as of 6 November 2026 that designation rests on Implementing Decision (EU) 2019/939 as renewed by Implementing Decision (EU) 2024/2120. Getting a UDI therefore takes two steps. The manufacturer receives its codes from a designated issuing entity, and it then assigns the UDIs to its own devices under that entity's rules. Each issuing entity sets the rules its codes follow, and MDCG 2019-1 (January 2019) gives guiding principles for the issuing entities' rules on the Basic UDI-DI.

An issuing entity commits to operate its UDI assignment system for at least 10 years after its designation (MDR Article 27(2)(e)(i)). That commitment reaches beyond the 5-year term of a single designation decision described below.

Who May Assign a UDI

Only the manufacturer may place the UDI on the device or its packaging (MDR Annex VI Part C Section 2.3). The manufacturer also keeps a list of all UDIs it has assigned in its technical documentation (MDR Article 27(7)). Importers and distributors, for their part, verify that a UDI has been assigned (MDR Articles 13(2)(d) and 14(2)(d)).

MDCG 2026-5, a position paper of July 2026 on UDI assignment between manufacturers and distributors, was listed in the Commission's updates on 22 July 2026. The paper refers to MDR Article 10(7), Article 27(1)(a)(i) and Annex VI Part C Sections 2.2 and 2.3, and on IVDR Articles 10(6) and 24. The positions of MDCG 2026-5 used on this page are listed below.

• Assignment: only the manufacturer may assign UDIs and receive codes from issuing entities.
• Distributors: a distributor must not obtain UDI-DIs in its own name.
• Own-brand products: their UDI-DIs are linked only to the manufacturer in EUDAMED and in the issuing entities' records.
• Delegation: practical tasks may be delegated by contract.

A person who assumes the obligations of a manufacturer under MDR Article 16(1), such as a distributor selling under its own brand, takes on all UDI duties and registers as manufacturer, as MDCG 2018-6 (October 2018) explains. The EU text says "manufacturer" throughout, where US pages speak of the "labeler". When an own-brand distributor becomes the manufacturer is set out under Article 16 MDR: when distributors and importers become manufacturers.

The Designation Decisions of 2019 and 2024

Until the Commission designated issuing entities, MDR Article 120(12) and IVDR Article 110(10) treated GS1, HIBCC and ICCBBA as designated issuing entities. That interim rule ended with the first Commission designation.

Commission Implementing Decision (EU) 2019/939 of 6 June 2019 (CELEX 32019D0939, OJ L 149, 7.6.2019, p. 73) designated issuing entities for 5 years from 27 June 2019, renewable for 5 years (Article 2(1)). Commission Implementing Decision (EU) 2024/2120 of 30 July 2024 (CELEX 32024D2120, OJ L, 2024/2120, 1.8.2024), in force since 1 August 2024, renewed the designation for the period from 27 June 2024 to 27 June 2029 (Article 1). The first term ended on 27 June 2024, and the renewal period starts on that same day, so the designation continued without a gap although the renewal was adopted on 30 July 2024. The designation therefore did not expire in 2024: it runs to 27 June 2029, the end of the renewal for 5 years that Article 2(1) of the 2019 decision allows.

How the UDI Appears on the Device: AIDC and HRI

The UDI carrier conveys the UDI in automatic identification and data capture (AIDC) form and, where applicable, as human readable interpretation (HRI), and the AIDC form can be a linear bar code, a 2D or matrix bar code or RFID (MDR Annex VI Part C Section 1). AIDC is the machine-readable form of the UDI, and HRI is the same UDI printed as legible characters. Both forms carry the same two parts, the UDI-DI and the UDI-PI.

The UDI carrier goes on the label of the device and on all higher levels of packaging, while shipping containers are excluded (MDR Article 27(4)). Because each packaging level has its own UDI-DI, the carrier on each level holds the UDI-DI of that level. On the label, the UDI carrier is point (h) of the 19 label particulars of MDR Annex I Section 23.2, which run from point (a) to point (s). Where a device's instructions for use are provided electronically under Implementing Regulation (EU) 2021/2226, the label also gives the access information, including the Basic UDI-DI and/or the UDI-DI (Article 6(1) and (3)). The other label particulars are covered under medical device labelling under the MDR and IVDR.

The UDI Dates: Labels and Direct Marking

The UDI carrier is required on labels in three steps by class under each regulation: under MDR Article 123(3)(f) from 26 May 2021 for implantable and class III devices to 26 May 2025 for class I, and under IVDR Article 113(3)(e) from 26 May 2023 for class D to 26 May 2027 for class A; reusable MDR devices also carry the UDI carrier on the device itself under the direct-marking dates of MDR Article 123(3)(g). The table sets out each class with its label date, its direct-marking date and the legal basis, as of 6 November 2026. Read by class, the table gives the UDI compliance dates under both regulations.

Not sure of the class? The medical device class finder gives an indicative class with the Annex VIII rule behind it.

The row that applies follows from the class of the device under Annex VIII of the regulation that covers it: the 22 rules of MDR Annex VIII for medical devices, and the 7 rules of IVDR Annex VIII for in vitro diagnostic devices. A reusable class IIb device, for example, has carried the UDI carrier on its label since 26 May 2023 and on the device itself since 26 May 2025.

Label Dates under MDR Article 123(3)(f)

Under MDR Article 123(3)(f), the UDI carrier has applied to implantable and class III devices since 26 May 2021, to class IIa and IIb devices since 26 May 2023 and to class I devices since 26 May 2025. The first step coincides with the MDR date of application, which Regulation (EU) 2020/561 set at 26 May 2021, and each later step follows 2 years after the one before, starting with implantable and class III devices.

As of 6 November 2026, every MDR class is therefore covered on the label. Class I devices have carried the UDI carrier on their labels since 26 May 2025; the date of 26 May 2027 concerns only the direct marking of reusable class I devices, which the next section explains. The exclusions set out in the section on devices outside the UDI system still apply to every MDR date, including the legacy-device position of MDCG 2021-25 rev.1. A class IIa device placed on the market in 2026, for example, carries the UDI carrier on its label and on every higher packaging level except the shipping container.

Direct Marking under MDR Article 123(3)(g)

Reusable devices must carry the UDI carrier on the device itself, and MDR Article 123(3)(g) staggers this direct marking: implantable and class III devices since 26 May 2023, class IIa and IIb devices since 26 May 2025 and class I devices from 26 May 2027. The three points (i), (ii) and (iii) of the article match the three label steps.

Each direct-marking date falls 2 years after the label date of the same class. As of 6 November 2026, reusable class I devices are the MDR group whose direct-marking date is still ahead. A reusable class I device placed on the market from 26 May 2027 therefore carries the UDI carrier on its label, as it has since 26 May 2025, and on the device itself. The conditions under which direct marking can be left out of the device are part of the carrier rules and belong to the carriers page listed in the detail table above.

Label Dates under IVDR Article 113(3)(e)

Under IVDR Article 113(3)(e), the UDI carrier has applied to class D devices since 26 May 2023 and to class B and C devices since 26 May 2025, and it applies to class A devices from 26 May 2027. The IVDR classes come from the 7 classification rules of IVDR Annex VIII under IVDR Article 47(1), which orders them from class A, the lowest risk, to class D, the highest. The IVDR steps follow the same order by risk as the MDR steps, highest class first, and each falls 2 years after the corresponding MDR label step.

IVDR Article 113(3)(e) sets no separate direct-marking date. As of 6 November 2026, class A is the IVDR class whose label date is still ahead, so manufacturers of class A in vitro diagnostic devices have until 26 May 2027 to place the UDI carrier on their labels. The exclusion of devices for performance studies under IVDR Article 24(1) applies to every IVDR date.

The UDI Database under MDR Article 28 and IVDR Article 25

The UDI database of MDR Article 28 and IVDR Article 25 holds each UDI-DI with its core data, while UDI-PIs and commercially confidential product information are kept out of it (MDR Article 28(2)). The core UDI data are accessible to the public free of charge under MDR Article 28(3). MDR Annex VI Part B lists 24 core data elements, and element 22 is the URL for additional information, such as electronic instructions for use. Implementing Regulation (EU) 2021/2226, as amended by Implementing Regulation (EU) 2025/1234, requires that URL for electronic instructions for use to be in the UDI database at the latest when device registration applies (Article 7(3)).

A change that does not require a new UDI-DI is updated in the UDI database within 30 days (MDR Annex VI Part C Section 5.8). A change on the Section 3.9 list leads to a new UDI-DI instead of an update. MDCG 2018-7 (October 2018) adds provisional considerations on the language issues of the UDI database.

As of 6 November 2026, the UDI database runs in the EUDAMED UDI/device registration module, which has been mandatory since 28 May 2026 under Commission Decision (EU) 2025/2371 of 26 November 2025, MDR Article 123(3)(d) and IVDR Article 113(3)(f). The decision was published in the Official Journal on 27 November 2025, and the obligations applied 6 months after publication. The module holds the Basic UDI-DI and UDI-DI records of the devices registered in it. How a device is registered is covered under device registration in EUDAMED.

Storing UDIs: Economic Operators and Health Institutions

Under MDR Article 27(8), economic operators store the UDI of class III implantable devices and of the devices determined by implementing act. The second group is open: the devices it covers are set by implementing act, so the duty can extend beyond class III implants without a change to MDR Article 27 itself.

Health institutions store the UDI of class III implantable devices under MDR Article 27(9). For other devices, member states encourage health institutions to store UDIs and may require it. A hospital that receives a class III implantable device therefore records its UDI, and storage for other devices depends on the member state.

Both storage duties add to the manufacturer's own list of assigned UDIs in the technical documentation (MDR Article 27(7)), so the identifier of a class III implant is recorded by the manufacturer, the economic operators and the health institution.

Supply-chain identification is a separate duty. MDR Article 25(2) and IVDR Article 22 require economic operators to identify their direct suppliers and their direct customers, including health institutions and healthcare professionals, for the period set in MDR Article 10(8). The two duties work together: the UDI says which device and which unit, and the supplier and customer records say where it came from and where it went. Each role's duties are set out under economic operators under the MDR and IVDR.

UDI Guidance Documents and Their Revisions

The MDCG has published UDI guidance on the Basic UDI-DI, systems and procedure packs, Article 16 responsibilities, database language issues, the IMDRF appendices, quality-system integration, the Q&A, the Master UDI-DI and the distributor question, and as of 6 November 2026 the Commission list shows each document with the revision in the table below. The 14 documents are listed with their subject and the revision and month shown on the Commission's list of MDCG guidance documents.

MDCG guidance is not legally binding (MDR Articles 103 and 105, IVDR Articles 98 and 99). Notified bodies take guidance and best practice documents into consideration under Annex VII Section 1.6.2 of each regulation. Two documents deal with systems and procedure packs (MDCG 2018-3 rev.1 and MDCG 2018-4), MDCG 2019-2 applies the UDI rules to the device part of the products in MDR Article 1(8), 1(9) and 1(10), and three documents (MDCG 2024-14 rev.1, MDCG 2025-7 rev.1 and MDCG 2025-8 rev.1) concern the Master UDI-DI. The documents explain how the MDCG reads Articles 27 to 29 of the MDR and Articles 24 to 26 of the IVDR, without changing the text of either regulation.

MDCG 2022-7 (May 2022) is the general Q&A on the UDI system, and MDCG 2026-5 (July 2026) carries the most recent date in the table. Every MDCG document by topic is listed under MDCG guidance.

UDI Status Summary

As of 6 November 2026, the UDI carrier is required on the labels of all MDR classes and of IVDR classes B, C and D, IVDR class A labels and direct marking of reusable MDR class I devices follow on 26 May 2027, and the designation of the issuing entities runs to 27 June 2029. Two changes stand out in 2026: the UDI/device registration module became mandatory on 28 May 2026, and MDCG 2026-5 set out the MDCG position on UDI assignment between manufacturers and distributors in July 2026.

What remains pending sits in the dates table above: manufacturers of class A in vitro diagnostic devices and of reusable class I medical devices are the two groups with a UDI date still ahead. Every other group has passed its label date, and its database records are kept current under the update rule described in the database section. The Master UDI-DI dates for contact lenses and spectacles follow their own delegated regulations and are set out on the Master UDI-DI page listed in the detail table.

What a UDI Does Not Show

A UDI identifies a device model, its packaging level and its production unit; it is not a certificate and not a statement that the device conforms. The two questions below mark that limit and set the EU system against the US one.

Does a UDI-DI in the Database Prove Conformity?

No: MDR Annex VI Part C Section 5 states that the presence of a UDI-DI in the UDI database shall not be assumed to mean that the device conforms to the Regulation. A database record shows that an identifier and its core data were registered, not that the device meets the requirements of the MDR or the IVDR. A buyer who checks a UDI-DI in the database learns which model it is, not whether it may be sold.

How the EU System Differs from the US System

The Basic UDI-DI is an additional EU requirement that the US UDI system does not have (MDCG 2022-7 Section C.2), and the US uses its own database, GUDID, instead of the EU UDI database. A UDI set-up built for the US market therefore needs the Basic UDI-DI and the EU database records added before EU registration. How the EU MDR and the FDA rules compare beyond UDI is set out in EU MDR vs FDA.