# EU MDR device classification How the 22 rules of Annex VIII place a device in Class I, IIa, IIb or III, how Rule 11 treats software, and what a notified body checks. Source: https://sted.digital/docs/standards/eu-mdr/classification · Last reviewed 17 October 2026 · Strand Standards and regulations EU MDR Article 51 places every device in Class I, IIa, IIb or III by intended purpose and risk, using the 22 rules of EU MDR Annex VIII: rules for non-invasive, invasive and active devices, then special rules. Where several apply, the strictest wins, and software follows Rule 11. The manufacturer classifies; the notified body checks. ## The requirement in plain English **Four classes (EU MDR Article 51(1)).** Class I is the lowest risk, Class III the highest. The class sets the conformity assessment route and how much evidence you need. **Definitions (Annex VIII, Chapter I).** Duration is counted as continuous use: transient is under 60 minutes, short term 60 minutes to 30 days, long term over 30 days. The chapter also defines invasive and surgically invasive devices, reusable surgical instruments, active devices for therapy or for diagnosis and monitoring, and the central circulatory and nervous systems. **How to apply the rules (Annex VIII, Chapter II).** Seven implementing rules govern every decision. The intended purpose decides, not the technology. Devices used together are classified separately, and an accessory has its own class. Software that drives or influences a device takes that device's class; standalone software is classified in its own right. A device used in several parts of the body is classified on its most critical use. If more than one rule applies, the strictest one gives the class. Interrupted use and immediate replacement count as continuous use. A device allows direct diagnosis when it gives the diagnosis itself or the decisive information for it. **The rules (Annex VIII, Chapter III).** Rules 1 to 4 cover non-invasive devices, starting at Class I and rising for devices that channel blood, change body fluids or treat wounds. Rules 5 to 8 cover invasive devices by body orifice, surgical access and duration; implants start at Class IIb and reach Class III near the heart or central nervous system. Rules 9 to 13 cover active devices: energy, diagnosis and monitoring, software, medicine delivery, and Class I for the rest. Rules 14 to 22 are special cases such as medicinal substances, nanomaterials, substances absorbed by the body and closed-loop systems. **Software (EU MDR Annex VIII Rule 11).** Software giving information for diagnostic or therapeutic decisions is Class IIa. It rises to IIb where a wrong decision could cause serious deterioration of health or surgery, and to III where it could cause death or irreversible deterioration. Monitoring physiological processes is IIa, or IIb for vital parameters where a change could mean immediate danger. All other software is Class I. **Class I sub-classes.** A Class I device that is sterile, has a measuring function or is a reusable surgical instrument (often written Is, Im and Ir) needs a notified body for those aspects only (EU MDR Article 52(7)). **Disputes (EU MDR Article 51(2)).** If you and your notified body disagree, the competent authority of your Member State decides. The class is your legal determination as manufacturer. Record your reasoning rule by rule, because your notified body will test it and your technical documentation must justify it (EU MDR Annex II, section 1.1). This is guidance to help you understand the requirement, not legal advice. ## What good looks like A 20-person digital health company makes two products: an app that flags possible atrial fibrillation from a wearable's ECG trace for a cardiologist to review, and the adhesive patch that records the trace. Its person responsible for regulatory compliance writes one classification rationale per product, three to five pages each. It opens with the intended purpose statement, copied word for word from the instructions for use, then the facts that drive the rules: invasiveness, duration, whether the device is active, whether it is software. It walks all 22 rules, each marked applies or does not apply with one line of reason, then the implementing rules that matter. For the app that means Rule 11 and implementing rule 3.3. The rationale weighs Class IIa against IIb and records why it lands on IIb: a missed diagnosis can delay treatment and lead to a stroke. It cites MDCG 2019-11 and MDCG 2021-24, the Medical Device Coordination Group's software and classification guidance. The head of clinical reviews each rationale and the managing director approves it. It sits in the technical documentation and is reopened through change control whenever the intended purpose, the claims or the target population change. Marketing copy goes through the same review, so the website never claims more than the classification assumed. ## Evidence an auditor expects - **Classification rationale** (required in the technical documentation): the notified body checks the class and the rule or rules applied, and that the reasoning matches the intended purpose. - **Qualification rationale** (required): why the product is a device at all, which the notified body reads before the class. - **Intended purpose, instructions for use and labelling**: the notified body checks that the class rests on the same words the user sees. - **Marketing material**: usual rather than required; a claim beyond the intended purpose can change the class, and auditors look at websites. - **Change control records**: show that a change to purpose, claims or design triggered a classification review. - **Guidance relied on**: MDCG documents and any Commission implementing act on the device type, cited where they decided a borderline call. ## Common mistakes ### Classifying the technology, not the intended purpose Two identical apps can sit in different classes because one is intended to inform a clinician and the other to make a diagnosis. Start from the intended purpose statement and keep every claim, including on your website, inside it. ### Stopping at the first rule that fits Rule 11 gives software a class, but Rules 10, 12 or 22 may also apply, and the strictest wins. Walk all 22 rules and record why each applies or not. ### Reading Rule 11 as "IIa by default" Many teams pick Class IIa because it is the rule's first sentence. The rule asks what harm a wrong decision could cause, so model the worst credible outcome for your patient population before you choose. ### Treating a hardware and software system as one device A companion app that drives a sensor takes the sensor's class, while a standalone analysis module is classified on its own, and accessories always have their own class. List every component and classify each one. ### Forgetting the Class I sub-class A Class I device supplied sterile or with a measuring function still needs a notified body for those aspects. Check sterility and measurement before you plan a self-declaration. ## How Sted helps For a medical device, Sted classifies it per market and shows the regulation, class and rule with the reasoning. The classification is information for you and your notified body or regulator to check, not a verdict. For the EU and Northern Ireland Sted's rules evaluate all 22 Annex VIII rules against your answers, compare the classes by rank and take the highest, refine a Class I result to Is, Im or Ir, and hold the result as pending only when an unanswered question could still raise the class. The class is information for you and your notified body to check, not a legal determination. For software Sted applies Rule 11 from two answers, how significant the information is to a diagnostic or therapeutic decision and how serious the patient's situation is, giving Class IIa, IIb or III, or Class I for software that informs no such decision; where a boundary is unclear on your answers it takes the higher class and says so. Sted classifies a medical device for the EU and Northern Ireland under EU MDR, Great Britain under UK MDR 2002, Canada under the Medical Devices Regulations (SOR/98-282), Australia under the Therapeutic Goods (Medical Devices) Regulations 2002, and the United States (from the FDA product code you confirm). Home raises one classification task per device product, whatever its markets: it asks whether the product is a medical device and how it works, facts every market's rules use, and gives an EU class only if the product is sold in the EU. A second task, for the other markets, follows when the product qualifies and is sold in any of them. Devices sold only in other markets get no class from Sted yet. After onboarding you can reopen your answers from Organisation → Summary. Which standards apply to you, and a device's class, are worked out by Sted's rules from your recorded answers; the AI model does not decide them. Sted does not classify a device legally. The manufacturer makes the Article 51 determination and the notified body checks it; Sted shows its working for both to test. ## Related guides and terms - [EU MDR](/docs/standards/eu-mdr): how classification fits with the rest of the regulation. - [Conformity assessment and notified bodies](/docs/standards/eu-mdr/conformity-assessment): the route your class leads to. - [UK MDR 2002 and UKCA marking](/docs/standards/uk-mdr-2002): Great Britain classifies under different rules, so software can land in a lower class there. - [How Sted decides what applies to you](/docs/product/classification-and-applicability): where Sted shows a device's class and its reasoning. - [ISO 13485 design and development](/docs/standards/iso-13485/design-and-development): the design inputs your intended purpose feeds. - [Applicability](/docs/glossary/applicability): the wider question of which rules reach your organisation. ## Frequently asked questions Q: Is all medical device software at least Class IIa under EU MDR? A: No. Rule 11 puts software at Class IIa or higher only when it provides information used for diagnostic or therapeutic decisions, or monitors physiological processes. Software that is a device but does neither, such as some patient-management or communication tools with a medical purpose, falls into Class I under the rule's last sentence. The question is what the software's output is used for, not how sophisticated it is. Q: Can a notified body disagree with my device's class? A: Yes. The notified body checks your classification as part of conformity assessment, and if the two of you cannot agree, the competent authority of the Member State where you have your registered place of business decides (EU MDR Article 51(2)). A clear rule-by-rule rationale in your technical documentation usually settles the question before it gets that far.