What changed from MDD to MDR, and what are the transition deadlines?

In short: MDR replaced the MDD with stricter classification (notably Rule 11 for software), deeper clinical-evidence expectations, mandatory PRRC and UDI, and tighter post-market surveillance. Legacy MDD certificates are in transition on two tiers under Regulation (EU) 2023/607: Class III and Class IIb implantable devices until 31 December 2027; other classes until 31 December 2028 — conditions attached. Status as of 21 July 2026 — confirm current transition dates before relying on this for planning, as deadlines have been extended and revised before.

The substantive changes, not just the name

MDR didn't just rebrand the MDD — it closed several gaps the older directive left open. Rule 11, the classification rule written specifically for software, is the most consequential for this audience: it moved most decision-support software from the MDD-era default of Class I into Class IIa or higher, bringing Notified Body review to products that previously self-certified. Clinical evidence expectations deepened across the board, with the clinical evaluation report becoming a more rigorously scrutinised document. MDR also introduced mandatory roles and systems that didn't exist under the MDD: the PRRC (Person Responsible for Regulatory Compliance), Unique Device Identification (UDI) for traceability, and a more structured post-market surveillance and vigilance system feeding into EUDAMED.

What "legacy certificate" means for you

If your device already held a valid MDD certificate, Regulation (EU) 2023/607 extended the transition on two tiers, not one: Class III and Class IIb implantable devices may continue to be marketed until 31 December 2027; other classes — Class IIa, non-implantable Class IIb, and Class I devices needing Notified Body involvement — until 31 December 2028. The extension is conditional, and two of the conditions are hard, dated gates that have already passed: a formal application had to be lodged with a Notified Body by 26 May 2024 and a written agreement signed by 26 September 2024. Beyond that, your quality management system must stay under surveillance and there must be no significant change to the device's design or intended purpose. A device that missed the 2024 gates is not covered by the extension at all, regardless of class. If your device relies on a legacy certificate, the tier and conditions attached to your certificate matter more than the general figures — verify against current Commission and MDCG guidance rather than a fixed date in any single article. (The December 2025 MDR/IVDR simplification proposal, COM(2025) 1023, is still a proposal under negotiation and does not move these transitional deadlines.)

Why this matters even for products with no MDD history

If you're building new, none of the transition provisions apply to you directly — you go straight to MDR requirements, including Rule 11 classification, from day one. The transition rules matter mainly if you're acquiring, partnering with, or evaluating a company that holds a legacy MDD certificate, where confirming what the transition actually still permits is a genuine due-diligence question.

Where next: MDR Annex VIII: How Device Classes Are Set · What is EUDAMED, and do I have to register?

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