MDCG 2020-3: Significant changes to legacy devices, explained
Which design or intended-purpose changes make your MDD device lose its transition-period grace — and which don't.
If your device is still on the market under an old MDD/AIMDD certificate, you may keep selling it during the MDR transition period — but only if you don't make "significant changes" to its design or intended purpose. MDCG 2020-3 defines what counts as significant. Cross the line, and your device needs full MDR certification before it can ship again.
Who this applies to
You are affected if you place devices on the EU market under a certificate issued under the old directives (MDD or AIMDD) and rely on the transitional provision of MDR Article 120(3) — extended to 2027/2028 by Regulation 2023/607. If all your devices are already MDR-certified, you can stop reading; this document no longer concerns you.
What counts as a significant change?
The guidance works through five flowcharts — a main chart and four sub-charts for intended purpose, design, software, and sterilisation/packaging changes. The pattern behind all of them:
Usually significant |
Usually not significant |
|---|---|
Extending the intended purpose to new indications, populations or body sites |
Administrative changes — manufacturer name, address, legal form |
Design changes that adversely affect safety or performance, including a new operating principle or a safety-relevant material change |
Narrowing the intended purpose or removing indications |
New or major operating-system or architecture changes; algorithm changes that affect device operation and may alter diagnosis or therapy |
Bug fixes, security updates and UI changes which do not negatively affect safety or performance |
Changing the sterilisation method or extending shelf life without validated data |
Changes that only correct a safety issue, agreed with your competent authority |
The edge cases live in the sub-charts. A change described as a "bug fix" can still be significant if it changes an algorithm in a way that affects device operation and may alter diagnosis or therapy. When in doubt, walk the flowchart and document the outcome.
What changed in Rev.1
Rev.1 (2023) aligned the guidance with Regulation 2023/607: the transition extension to 2027/2028 and the removal of the certificate "sell-off" deadline. Conditions now reference Article 120(3a)–(3e); the substance of what counts as a significant change did not change.
What this means for you, practically
- Assess every change against the flowcharts before implementing it — not after. Attach the completed flowchart path to the change record.
- Document non-significance explicitly. Your notified body will sample change records during surveillance audits; "we considered it not significant" without reasoning won't survive one.
- Wire it into your change management SOP. A single extra field — "Article 120(3) assessment" — in your change form covers most of this.
- Plan the exit. If a change you actually need is significant, that's your trigger to schedule full MDR certification rather than working around it.
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