Under MDR Article 20 and Annex V, the CE mark must be affixed visibly, legibly, and indelibly to the device or its sterile packaging, to the sales packaging, and to the instructions for use. It must follow the proportions shown in Annex V, be at least 5 mm in height (with limited exceptions for small devices), and — when a Notified Body was involved in conformity assessment — be followed by the Notified Body's four-digit identification number.

By Tibor Zechmeister and Felix Lenhard. Last updated 2026-04-10.

TL;DR

  • The CE mark rules for medical devices are set by MDR Article 20 and Annex V of Regulation (EU) 2017/745 — not by the old Directive 93/68/EEC text that many legacy suppliers still send around.
  • The mark must be affixed visibly, legibly, and indelibly to the device (or its sterile pack), to the sales packaging, and to the instructions for use.
  • The minimum height is 5 mm. Smaller dimensions are only allowed where the device itself is too small to accommodate it.
  • If a Notified Body took part in the conformity assessment, the four-digit NB identification number must appear immediately next to or after the CE mark.
  • Class I self-certified devices carry the CE mark alone, with no NB number. Putting a number next to a self-certified Class I device is a serious labeling defect.
  • The proportions shown in Annex V are mandatory when scaling: the "C" and "E" are drawn on a grid and the ratio must be kept when the mark is enlarged or reduced.
  • Wrong CE mark formatting is one of the most common non-conformities a Notified Body or competent authority will flag in a first audit, and one of the easiest to fix before it becomes a finding.

Why this matters for your startup

A Class IIa wearable I worked with had done everything right. Good technical file. Clean clinical evaluation. QMS audit passed on the first attempt. Then the Notified Body's final review flagged the label artwork: the CE mark had been pulled from a supplier's generic template, the "C" and "E" were slightly off-proportion, the mark was 3.5 mm high on the primary pack, and the Notified Body number sat two lines below the mark separated by the product name. Three findings. Three weeks to re-lay the artwork, re-print pilot stock, and re-run label verification. All because nobody on the team had ever read Annex V of the MDR with their own eyes.

The CE mark is the most visible output of the entire certification process. Regulators, buyers, distributors and customs officers all see it before they see anything else. A mark that is the wrong size, wrong shape, in the wrong place, or carrying the wrong accompanying number tells anyone who knows what they are looking at that your labeling system is not under control. And labeling is where auditors look first, because it is cheap to check and expensive to get wrong.

This post is the rule set. Read it once, build your artwork to it, and move on.

What Article 20 actually says

MDR Article 20 is titled "CE marking of conformity" and sets the core rules. Three of them matter for your artwork:

"The CE marking shall be subject to the general principles set out in Article 30 of Regulation (EC) No 765/2008." — Regulation (EU) 2017/745, Article 20, paragraph 1.

"The CE marking shall be affixed visibly, legibly and indelibly to the device or its sterile packaging. Where such affixing is not possible or not warranted on account of the nature of the device, the CE marking shall be affixed to the packaging. The CE marking shall also appear in any instructions for use and on any sales packaging." — Regulation (EU) 2017/745, Article 20, paragraph 3.

"The CE marking shall be followed by the identification number of the notified body responsible for the conformity assessment procedures set out in Annex IX, Annex X or Annex XI, where applicable." — Regulation (EU) 2017/745, Article 20, paragraph 5.

And Article 20, paragraph 6 adds that the NB identification number must itself be affixed by, or under the responsibility of, the manufacturer.

Three things to take from the Article 20 text:

  1. The mark goes on the device (or sterile pack), on sales packaging, and in the IFU. Not "one of the above" — all of them, unless the device's nature makes affixing on the device impossible.
  2. "Visibly, legibly, indelibly" is the legal test. It is not decorative language. Indelibly means the mark survives the expected conditions of use and handling: cleaning, wiping, sterilization cycles, sun exposure, transport.
  3. The Notified Body number is not an optional adornment. When an NB was involved in the conformity assessment under Annex IX, X or XI, their four-digit number is a mandatory part of the mark.

What Annex V actually says (form and proportions)

Annex V of the MDR is short. It contains the graphic of the CE marking and the rule that governs its proportions:

"If the CE marking is reduced or enlarged the proportions given in the above graduated drawing must be respected." — Regulation (EU) 2017/745, Annex V, second paragraph.

"The various components of the CE marking must have substantially the same vertical dimension, which may not be less than 5 mm. This minimum dimension may be waived for small-scale devices." — Regulation (EU) 2017/745, Annex V.

Unpacked:

  • Proportions are fixed. The "C" and the "E" are drawn on a square grid. When you scale the mark up or down you must scale proportionally. You cannot stretch the "E" to fit a narrow label. You cannot slim the "C" to save millimetres. Artwork teams routinely get this wrong because they pull a bitmap off the internet and rescale it non-proportionally.
  • Minimum height is 5 mm. Both characters must be substantially the same vertical dimension, and that dimension must be at least 5 millimetres.
  • Small-device waiver. If the device itself is physically too small to carry a 5 mm mark, the minimum may be reduced — but only on the device itself. The sales packaging and the IFU still carry the full-size mark. This is the exception, not the rule. Do not use it because your label "feels crowded."

The CE logo you use should be a clean vector file drawn to the Annex V proportions. Most regulatory affairs teams keep a single approved master file and forbid designers from using anything else. That is a five-minute SOP that prevents an entire class of findings.

The Notified Body number — when, where, how

Whether you print a four-digit number next to the CE mark depends on one thing: was a Notified Body involved in the conformity assessment of your device?

  • Class I (self-certified — non-sterile, non-measuring, non-reusable surgical, non-Ir): no NB involvement, no number next to the CE mark. Putting a number there is a labeling error that signals to any auditor that your classification and conformity assessment logic is confused.
  • Class Is, Im, Ir, and all Class IIa, IIb, III devices: an NB was involved under Annex IX, X or XI. The mark must be followed by that NB's four-digit identification number. For Class Is, Im, Ir the NB's involvement is limited to specific aspects (sterilisation, metrology, reprocessing), but the number is still required on the label.

On placement: Article 20(5) says the CE marking "shall be followed by" the NB identification number. In practice this means the number sits immediately next to or directly after the CE mark, visually paired with it. It should not be on a separate line with other text between them. It should not be smaller to the point of illegibility. It should read as one unit with the CE mark.

On the number itself: it is always a four-digit number. You find your NB's number in the NANDO database maintained by the European Commission. Use the number exactly as NANDO lists it. Do not add "NB", do not add "No.", do not localise it. Just the four digits.

Where the mark goes — label, packaging, IFU

Article 20(3) is specific. The mark must appear in three locations:

  1. On the device itself, or on its sterile packaging. If the device is non-sterile, the mark goes on the device wherever it is technically feasible and appropriate. If the device is sterile, the mark goes on the sterile barrier packaging — because that is the packaging the user opens and handles at the point of use.
  2. On any sales packaging. The outer commercial pack the customer buys. If you have multiple levels of outer packaging (shelf box, shipping case), the mark goes on the sales packaging — the level at which the device is sold.
  3. In the instructions for use. Every IFU, whether paper or electronic, must show the CE mark. For eIFU under Implementing Regulation (EU) 2021/2226, the mark appears in the electronic document.

A common mistake is thinking "the mark is on the device, that is enough." It is not. The IFU and the sales packaging are independent, mandatory locations. A missing CE mark on the IFU is a finding, full stop.

Test: compliant vs non-compliant

Here are five label configurations. Three are wrong.

Configuration A. Class IIa electrosurgical generator. CE mark 8 mm high, correct Annex V proportions, immediately followed by "0123" (the NB's four-digit number), matched vertical height with the CE mark. Mark and number placed in the top right of the primary label. Same mark present on the outer carton and in the IFU. → Compliant.

Configuration B. Class I non-sterile, non-measuring reusable manual instrument. CE mark 6 mm high, correct proportions, no number. Mark on the device (laser-etched), on the sales packaging, and in the IFU. → Compliant.

Configuration C. Class I sterile wound dressing. CE mark 5 mm high on the sales packaging, no NB number. → Non-compliant. Class Is requires NB involvement for sterilisation aspects and the NB's four-digit number must appear next to the CE mark.

Configuration D. Class IIb implantable loop recorder. CE mark 4 mm high on the sterile pouch, NB number "1234" on a separate label panel 3 cm away from the mark. → Non-compliant. Minimum height is 5 mm and the implant pouch is not "small-scale" in a way that clearly warrants the waiver; the NB number is also detached from the CE mark rather than following it.

Configuration E. Class IIa SaMD distributed as a downloadable app. CE mark shown in the "About" screen of the software with the NB number, and repeated in the electronic IFU and on the sales / distribution page. → Compliant (for software the "device" and its "packaging" are interpreted in line with the nature of the product; the mark must still appear visibly, in the IFU, and on whatever serves as commercial packaging).

Ship: the label artwork playbook

This is the sequence we use with startups to get label artwork right the first time.

  1. Lock your CE logo master file. One approved vector file, drawn to Annex V proportions, under document control in your QMS. No designer touches anything else.
  2. Lock your NB number. Pull the four digits from NANDO, record the date of the pull, put the number into your label specification as a controlled data element. If you change NB, this is a controlled change.
  3. Write a labeling specification for every SKU that states: CE mark minimum height, exact placement zone, NB number presence and position, label substrate, and the indelibility test used to verify the artwork survives use conditions.
  4. Run indelibility verification. Before the label goes into production, verify the print survives the conditions the regulation requires: cleaning, sterilisation if relevant, transport, storage, sunlight. Document the verification in the technical file.
  5. Apply the mark in all three locations. Device or sterile pack, sales packaging, IFU. Check each physically before sign-off.
  6. Have a second pair of eyes check against Annex V. Not the designer. Not the product owner. A regulatory reviewer who opens the Annex V text and compares it to the artwork line by line.
  7. Freeze the artwork in a controlled document. Label artwork is a controlled design output. Any change after freeze is a design change and follows your change control process. This is the rule that prevents well-meaning marketing teams from "refreshing" the label six months after launch and quietly breaking compliance.

This is a one-day SOP that eliminates an entire class of audit findings.

Reality Check — where do you stand?

Answer honestly. For every "no," add the action to your next sprint.

  1. Do you have a single, controlled CE logo master file drawn to Annex V proportions, referenced from your labeling specification?
  2. Is the CE mark on your current artwork at least 5 mm high on device, sales packaging and IFU — and can you justify any reduction with a small-device rationale in your technical file?
  3. If your device required NB involvement, does the four-digit NB number appear immediately next to or after the CE mark on all three locations?
  4. If your device is Class I self-certified, have you verified that there is no NB number anywhere near the CE mark?
  5. Have you run and documented indelibility testing of the mark under real use conditions?
  6. Is your label artwork frozen as a controlled design output, with a change-control process for any future updates?
  7. Has a regulatory reviewer (not the designer) compared the artwork against the Annex V text line by line and signed off?

Three or more "no" answers means your labeling system is a finding waiting to happen. Fix it before your next audit, not after.

Frequently Asked Questions

What is the minimum size of the CE mark on a medical device under MDR? Annex V of Regulation (EU) 2017/745 sets the minimum vertical dimension at 5 mm. A smaller mark is only allowed where the device itself is too small to accommodate a 5 mm mark. The sales packaging and the instructions for use must still carry the full-size mark.

Do I need a Notified Body number next to the CE mark on a Class I medical device? Only if the Class I device involved a Notified Body in its conformity assessment. That covers Class Is (sterile), Im (measuring function), and Ir (reusable surgical instruments). Plain Class I self-certified devices carry the CE mark alone. Adding an NB number to a self-certified Class I device is a labeling error.

Where exactly does the Notified Body number go? Article 20(5) of MDR says the CE marking "shall be followed by" the NB identification number. In practice that means the four digits sit immediately next to or directly after the CE mark, visually paired with it, at roughly the same height. It should read as one unit with the mark, not as a separate label element.

Can I stretch or reshape the CE mark to fit my label layout? No. Annex V requires the proportions of the graduated drawing to be respected when the mark is enlarged or reduced. You scale proportionally, period. A stretched or reshaped CE mark is not a CE mark.

Does the CE mark have to appear in the instructions for use? Yes. MDR Article 20(3) requires the CE mark to appear on the device or its sterile packaging, on any sales packaging, and in any instructions for use. All three locations are mandatory.

Which article governs CE marking of medical devices under MDR? MDR Article 20 governs CE marking, and Annex V shows the form and proportions of the mark. The broader general principles of CE marking across EU product legislation are set by Article 30 of Regulation (EC) No 765/2008, which Article 20(1) of the MDR points to.

Sources

  1. Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, Article 20 ("CE marking of conformity") and Annex V ("CE marking of conformity"). Consolidated text on EUR-Lex.
  2. Regulation (EU) 2017/745, Article 18 (Implant card) and Annex I, Chapter III (Information supplied with the device) — for the labeling context around the CE mark.
  3. Regulation (EC) No 765/2008 of the European Parliament and of the Council setting out the requirements for accreditation and market surveillance, Article 30 (General principles of the CE marking) — referenced by MDR Article 20(1).
  4. NANDO database (New Approach Notified and Designated Organisations), European Commission — authoritative source for the four-digit identification numbers of Notified Bodies designated under MDR.

This post is part of the Technical Documentation & Labeling series in the Subtract to Ship: MDR blog. Authored by Felix Lenhard and Tibor Zechmeister. For startup-specific regulatory support on label artwork review and conformity assessment, see Zechmeister Strategic Solutions.