Substantial modification: when a change makes you the manufacturer
Under Regulation (EU) 2023/1230, a substantial modification is a change to a machine, by physical or digital means, made after it was placed on the market, not foreseen by the manufacturer, that creates a new hazard or increases an existing risk so that new safeguards are needed. Whoever makes such a modification is treated as the manufacturer of the modified machine and takes on the full manufacturer obligations for it.
This is general information about Regulation (EU) 2023/1230, verified as at 12 July 2026, not legal advice. Confirm the definition and article number against the final text.
Why the concept exists
Machines are routinely rebuilt, retrofitted, re-tooled and re-programmed years after they were first sold. The Regulation makes explicit what has long been debated: once a change goes beyond normal maintenance and materially alters the machine's safety, the machine is effectively new, and someone has to answer for it. That someone is the party who made the change.
The three tests
A modification is substantial when all of the following hold:
- It happens after the machine was placed on the market, by physical or digital means, including a software change.
- It was not foreseen by the original manufacturer, so it is outside what the manufacturer designed and documented for.
- It creates a new hazard or increases an existing risk to the point that new protective measures or safeguards are needed.
Routine maintenance, like-for-like replacement of a worn part, or a change the manufacturer already anticipated and documented, is not a substantial modification. The line is whether the safety picture changed in a way the original manufacturer did not account for.
What happens if it is substantial
The party who made the modification becomes the manufacturer of the modified machine. That means the full set of obligations attaches to the modified machine: a fresh conformity assessment for the parts affected, an updated technical file, a new EU declaration of conformity, the CE marking, and instructions. If the modification pushes the machine into an Annex I category, the corresponding conformity route follows, which can mean a notified body where none was needed before. See when a notified body is mandatory.
Who this catches
This is the rule integrators, in-house engineering teams and refurbishers most need to watch. If you assemble a line from several machines, retrofit a robot cell, or push a software update that changes a safety function, you may have become the manufacturer of the result. The same logic sits behind the deeming rule for importers and distributors: place a machine on the market under your own name or trademark, or modify it in a way that affects compliance, and you take on the manufacturer's duties.
Check where a modification leaves you
The report reflects your operator role, including integrator or modifier, and flags where substantial modification would make you the manufacturer and which conformity route the modified machine would then face.
Get my machinery report →Sources
- Regulation (EU) 2023/1230, substantial modification and operator deeming (definitions and Article 18, to be confirmed against the final text). EUR-Lex (checked 12 July 2026).
- Substantial modification and the manufacturer deeming rule: TUV Rheinland; EFS Consulting (checked 12 July 2026).