Substantial Modification of Machinery: The Article 3(16) Test, Retrofits and When You Become the Manufacturer

The one exception is a non-professional user who modifies their own machinery for their own use.

Article 3(16) and Article 18 apply from 20 January 2027, when the Regulation replaces Directive 2006/42/EC. The Directive applies until 19 January 2027 through national transpositions and contains no definition of the term, so the four-condition test is new law under the EU Machinery Regulation.

The sections below cover the four conditions, the exclusions, Article 18, a six-step retrofit check, the duties that follow and the Directive reasoning. Seven core rules are tabled below.

What Is a Substantial Modification of Machinery?

Article 3(16) of Regulation (EU) 2023/1230 defines a substantial modification as "a modification of machinery or a related product, by physical or digital means after that machinery or related product has been placed on the market or put into service, which is not foreseen or planned by the manufacturer, and which affects the safety of that machinery or related product, by creating a new hazard, or by increasing an existing risk", where that hazard or risk requires one of two kinds of new protective measures.

The definition in the Regulation (EU) 2023/1230 text on EUR-Lex decides who carries the manufacturer's obligations for the changed machine. Directive 2006/42/EC has no such definition, so the term enters EU machinery law on 20 January 2027, next to the other obligations under the Machinery Regulation.

The Four Conditions of Article 3(16)

Article 3(16) is met only when all four of its conditions apply together: a change after placing on the market or putting into service, not foreseen or planned by the manufacturer, with an effect on safety, which requires the protective measures named in points (a) or (b).

The four conditions are compared below with the question each one puts to a planned change.

All Article 3 terms: Machinery Regulation definitions.

Point (a) covers "the addition of guards or protective devices to that machinery or related product the processing of which necessitates the modification of the existing safety control system".

Point (b) covers "the adoption of additional protective measures to ensure the stability or mechanical strength of that machinery or related product". By that wording, a new hazard that the existing protective measures already deal with requires neither measure, so the fourth condition is not met.

Physical and Digital Changes, Including Software

A substantial modification can be made "by physical or digital means", so a software change counts in the same way as a mechanical rebuild once the other three conditions are met. The Commission's Blue Guide applies its test for modified products to software updates too.

Annex III, section 1.1.9 of Regulation (EU) 2023/1230 states: "The machinery or related product shall collect evidence of a legitimate or illegitimate intervention in the software or a modification of the software installed on the machinery or related product or its configuration."

That evidence helps a later modifier show which software state and configuration were assessed before the change. The requirement is part of the protection against corruption (Annex III 1.1.9).

What Does Not Count: Repair, Maintenance and Foreseen Changes

Repair and maintenance operations that do not affect compliance with the essential health and safety requirements are not substantial modifications, as recital 26 of Regulation (EU) 2023/1230 states.

Article 3(34) defines lifetime as the period from placing on the market or putting into service until the machinery is discarded, "including ... the phases of transport, assembly, dismantling, disabling, scrapping or other physical or digital modifications foreseen by the manufacturer".

A change the manufacturer foresaw, for example an option or update it describes in its instructions, therefore falls outside Article 3(16) by its own words. A change that creates no new hazard and increases no existing risk also falls outside it.

Article 18: When the Modifier Becomes the Manufacturer

Under Article 18 of Regulation (EU) 2023/1230, a natural or legal person who carries out a substantial modification is considered a manufacturer and takes on the manufacturer's obligations under Article 10 for the modified machinery or related product.

A plant operator, an integrator and a service firm alike become the manufacturer when they make the change. Article 10 sets out the full list of manufacturer obligations under the Machinery Regulation.

Article 25(1) names the person referred to in Article 18, next to the manufacturer, as the one who applies the conformity assessment procedure, and Article 18 points to Article 25(2), (3) or (4) for the modified product. Article 17 sets a separate trigger for importers and distributors, which does not depend on Article 3(16).

Modifying One Machine Within a Larger Installation

When a substantial modification affects only one machine or related product that is part of an assembly, the modifier is the manufacturer of that affected machine, "as demonstrated in the risk assessment" (Article 18, first paragraph). The Article 10 obligations then attach to the affected machine, not to every machine of the line.

The risk assessment therefore fixes the scope of the new obligations, and it has to show where the effect of the change ends.

Article 3(1)(d) of Regulation (EU) 2023/1230 treats machines or partly completed machines that are arranged and controlled to function as an integral whole as one machine. How combined machines become one machine is explained under assemblies of machinery.

The Exception for Non-Professional Own Use

A non-professional user who substantially modifies their own machinery for their own use is not a manufacturer under Article 18, third paragraph. The exception names only the non-professional user.

Article 3(18)(b) makes a person who manufactures machinery and puts it into service for its own use a manufacturer, and Article 3(36) defines a professional user as "a natural person who uses or operates machinery or a related product in the course of professional activity or work".

How to Assess a Retrofit Step by Step

Assessing a planned retrofit under Regulation (EU) 2023/1230 takes six steps, from checking what the original manufacturer foresaw to applying the conformity assessment procedure for the modified machine. The six steps are listed below in the order in which they are run.

1. Check the instructions and documentation for changes the manufacturer foresaw or planned (Article 3(34)).
2. Run a risk assessment of the machine in its modified state, using the five steps (a) to (e) of Annex III, Part B, point 1 (machinery risk assessment).
3. Test each new hazard or increased risk against points (a) and (b) of Article 3(16): guards or protective devices that require a change to the existing safety control system, or additional measures for stability or mechanical strength.
4. Record the reasoning, as a matter of practice, when neither point applies: the change is then not a substantial modification and Article 18 does not attach.
5. Fix the scope: the whole machine, or only the affected machine within an installation, as demonstrated in the risk assessment (Article 18).
6. Take on the Article 10 duties and apply the Article 25 procedure for the category of the modified product, which the machinery conformity route finder shows.

What Follows a Substantial Modification: Procedure, Documents and CE Marking

A person who carries out a substantial modification applies the Article 25 conformity assessment procedure to the modified machine, draws up its technical documentation and EU declaration of conformity, and affixes the CE marking, as Article 10(2) of Regulation (EU) 2023/1230 requires of every manufacturer. The route follows the category of the product.

Machinery listed in Annex I, Part A uses module B + C, module H or module G, never module A (Article 25(2)).

Machinery listed in Annex I, Part B uses module A only where it is designed in accordance with harmonised standards or common specifications specific to that category covering all relevant essential health and safety requirements, and otherwise module B + C, H or G (Article 25(3)). All other products use module A (Article 25(4)).

The modifier keeps the technical documentation and the EU declaration of conformity for at least 10 years after the modified machine is placed on the market or put into service (Article 10(3)). The six duties are compared below.

Before 20 January 2027: No Definition, Only De Facto New Machinery

Directive 2006/42/EC contains no definition of substantial modification, and Annex XII of Regulation (EU) 2023/1230 lists no Directive counterpart for Article 18. Until 19 January 2027 the Directive applies through national transpositions, and whether a modified machine counts as new rests on Commission guidance under the Machinery Directive 2006/42/EC.

The Commission's machinery page states that the Directive applies "when existing machinery is modified to such extent that it becomes de facto new machinery". The Commission's Guide to application of the Machinery Directive 2006/42/EC, Edition 2.3 (April 2024), gives no precise criteria for that point and refers doubtful cases to the national authorities.

The Blue Guide on the implementation of EU product rules 2022, Commission Notice 2022/C 247/01, is guidance without legal effect.

It treats a modified product as new when three conditions are met: its original performance, purpose or type is modified in a way not foreseen in the initial risk assessment; the nature of the hazard has changed or the level of risk has increased; and it is made available or put into service. The Blue Guide applies the same test to software updates.

A machine placed on the market with a Directive declaration needs no new declaration under the Regulation unless it is substantially modified.

Products placed on the market under the Directive before 20 January 2027 may continue to be made available (Article 52(1)), and there is no parallel period in which either act may be chosen. Every date is set out in the Machinery Regulation timeline.

Modified Machines, Resale and Workplace Rules

Three neighbouring rules decide what else applies to a modified machine: the Article 17 trigger for importers and distributors, the rules for second-hand machinery, and the workplace rules for its use. The three rules are listed below.

• Importers and distributors: under Article 17 of Regulation (EU) 2023/1230, an importer or distributor that places a product on the market under its own name or trademark, or modifies a product already placed on the market in such a way that compliance may be affected, is considered a manufacturer, a lower threshold than Article 3(16); see distributor obligations for machinery.
• Second-hand imports: products, whether new or second-hand, imported from a third country are covered when they are first placed on the Union market (recital 10); see used machinery and the Machinery Regulation.
• Workplace rules: Article 5 lets Member States protect persons, including workers, when installing or using machinery, "provided that such rules do not allow for the modification of machinery or a related product in a way that is not compatible with this Regulation"; employer duties are compared under Machinery Regulation and the Work Equipment Directive.

Substantial Modification Questions

Three questions recur once a modification is classed as substantial: whether a notified body is needed, how long the technical documentation is kept and whether machines already in use must be upgraded.

Does a substantially modified machine need a notified body?

Only where Article 25 requires one for the product's category: Annex I, Part A machinery always goes through a notified body (module B + C, H or G), Annex I, Part B machinery follows Article 25(3), and products outside Annex I use module A (internal production control). Annex I of Regulation (EU) 2023/1230 lists 25 categories, 6 in Part A and 19 in Part B, as set out under high-risk machinery (Annex I).

How long does the modifier keep the technical documentation?

At least 10 years after the modified machine is placed on the market or put into service, together with the EU declaration of conformity (Article 10(3)). Directive 2006/42/EC counted the period from the date of manufacture or, for series manufacture, of the last unit produced.

Must machines already in use be upgraded?

No: Regulation (EU) 2023/1230 creates no retrofit obligation for machines already placed on the market or put into service. Their use is governed by workplace law, and the manufacturer duties of the Regulation attach only when someone makes a substantial modification (Article 18).