---
title: "EU Machinery Regulation: when does a modification constitute substantial modification?"
canonical_url: "https://www.sorena.io/artifacts/eu/machinery-regulation/substantial-modification"
source_url: "https://www.sorena.io/artifacts/eu/machinery-regulation/substantial-modification"
author: "Sorena AI"
description: "Guide to substantial modification under Regulation (EU) 2023/1230: change triggers, risk assessment, EHSRs, technical documentation, conformity assessment, CE marking, and records."
published_at: "2026-05-09"
updated_at: "2026-05-09"
keywords:
  - "EU Machinery Regulation"
  - "Regulation (EU) 2023/1230"
  - "substantial modification"
  - "risk assessment"
  - "conformity assessment"
  - "CE marking"
---
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# EU Machinery Regulation: when does a modification constitute substantial modification?

Guide to substantial modification under Regulation (EU) 2023/1230: change triggers, risk assessment, EHSRs, technical documentation, conformity assessment, CE marking, and records.

*Artifact Guide* *EU*

## EU Machinery Regulation substantial modification

Use this guide when a physical or digital change to machinery or a related product could change the safety case after it has been placed on the market or put into service.

The key question is whether the change creates a new hazard, increases an existing risk, or requires protective measures that make the modifier responsible for a new manufacturer-level conformity file.

A substantial modification assessment under Regulation (EU) 2023/1230 should begin with the modification facts, not a generic maintenance checklist. Capture what changed, whether the original manufacturer foresaw it, how the hazards or risks changed, and whether Article 18 makes the person carrying out the change responsible as the manufacturer for the affected machinery or related product.

## When a change can become a substantial modification

Article 3(16) defines substantial modification as a physical or digital change made after machinery or a related product has been placed on the market or put into service, where the change was not foreseen or planned by the manufacturer and affects safety by creating a new hazard or increasing an existing risk.

The threshold is not met just because machinery is repaired, serviced, or updated. The file should show whether the change affects compliance with the relevant essential health and safety requirements in Annex III and whether it requires one of the protective responses described in the Regulation.

- Record the baseline product, model, configuration, serial range, instructions, intended use, limits of use, existing safeguards, and original conformity evidence.
- Classify the change as mechanical, electrical, control-system, software, firmware, guard, protective-device, stability, load, speed, operating-mode, operating-environment, or safety-function related.
- Check whether the change was foreseen or planned by the manufacturer in the original design, instructions, limits of use, update policy, or technical documentation.
- Treat the threshold as unresolved until the risk assessment shows whether new hazards or increased risks exist and whether additional protective measures are needed.

Sources for this answer:

- [Regulation (EU) 2023/1230 on machinery](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A02023R1230-20230629&ref=sorena.io) - Grounds the Article 3 substantial-modification definition and the Article 18 consequences for the person carrying out the change.
- [European Commission machinery sector page](https://single-market-economy.ec.europa.eu/sectors/mechanical-engineering/machinery_en?ref=sorena.io) - Commission machinery context explains that existing machinery can be modified to such an extent that it becomes de facto new machinery.

## Risk assessment drives the decision

The substantial-modification decision should be traceable to a risk assessment. Identify the hazards introduced by the modification, estimate and evaluate the changed risks, decide whether safeguards or information for use reduce the risks sufficiently, and verify that the modified machinery still meets the applicable Annex III EHSRs.

For machinery that is part of an assembly, document the affected boundary. Article 18 links the modifier's obligations to the affected machinery or related product, so the risk assessment should explain why any other machinery or related products in the assembly are unaffected.

- Look for new hazards from changed motion, access, energy, load, stability, control logic, safety-related software, cybersecurity exposure, operator interaction, maintenance method, or foreseeable misuse.
- Look for increased risks where severity, probability, exposure, avoidability, reliability, stability margin, mechanical strength, stopping behavior, or safeguard effectiveness changes.
- Check whether guards or protective devices must be added and whether their processing requires modification of the existing safety control system.
- Check whether additional protective measures are needed to ensure stability or mechanical strength.
- Keep a non-substantial conclusion only where the evidence shows repair or maintenance does not affect compliance with the relevant EHSRs.

Sources for this answer:

- [Regulation (EU) 2023/1230 on machinery](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A02023R1230-20230629&ref=sorena.io) - Article 3(16) ties substantial modification to new hazards, increased existing risks, and specified protective-measure triggers.
- [ISO 12100:2010 - Safety of machinery](https://www.iso.org/obp/ui/en/?ref=sorena.io#!iso:std:51528:en) - Supports using hazard identification, risk estimation, risk evaluation, risk reduction, documentation, and verification as the assessment method.

## What changes when the threshold is met

If the change is a substantial modification, Article 18 treats the person carrying out it as the manufacturer for the affected machinery or related product. The modifier should then run the manufacturer obligations for that affected scope instead of closing the work as ordinary service or maintenance.

That means the modified machinery or related product needs a refreshed compliance file: applicable Annex III EHSRs, technical documentation, conformity assessment, EU declaration of conformity, CE marking, instructions, safety information, and records that explain the affected boundary.

- Name the natural or legal person that carried out the substantial modification and define the affected machinery or related product.
- Update the EHSR matrix for the modified design, construction, safeguards, control functions, software, instructions, and safety information.
- Draw up or update the technical documentation set out in Annex IV Part A for the affected machinery or related product.
- Apply the Article 25 conformity assessment route that fits the modified product category and any Annex I status.
- Draw up or update the EU declaration of conformity and affix CE marking only after conformity with the applicable requirements has been demonstrated.

Sources for this answer:

- [Regulation (EU) 2023/1230 on machinery](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A02023R1230-20230629&ref=sorena.io) - Article 18 treats the person carrying out a substantial modification as the manufacturer and Article 10 grounds the resulting manufacturer obligations.
- [EUR-Lex summary - machinery safety requirements](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=LEGISSUM%3A4804067&ref=sorena.io) - Official summary supports the EHSR, conformity assessment, EU declaration of conformity, CE marking, safety information, and instructions overview.

## Conformity assessment and CE marking

The conformity assessment should be selected for the modified product, not copied from the original file without review. Article 25 distinguishes products outside Annex I, Annex I Part A products, and Annex I Part B products, with different routes depending on whether harmonised standards or common specifications cover all relevant EHSRs.

For Annex I Part A machinery or related products, plan for a conformity assessment route involving a notified body. For Annex I Part B, internal production control is available only where the modified product was designed and constructed according to harmonised standards or common specifications that cover all relevant EHSRs; otherwise, use the notified-body routes identified in Article 25. Products not listed in Annex I use internal production control.

- Record the Annex I screening result and the reasons for the selected Article 25 route.
- List the harmonised standards or common specifications used and map exactly which EHSRs they cover.
- Keep notified-body applications, reports, certificates, quality-system approvals, or unit-verification evidence where the route requires them.
- Do not affix or rely on CE marking for the modified product until the conformity assessment has demonstrated compliance.
- Make the EU declaration of conformity available with the modified product, or provide the internet address or machine-readable code where the declaration can be accessed as allowed by the Regulation.

Sources for this answer:

- [Regulation (EU) 2023/1230 on machinery](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A02023R1230-20230629&ref=sorena.io) - Articles 21, 24, and 25 ground EU declarations of conformity, CE marking, and the conformity assessment route selection.
- [Single Market Compliance Space - notified bodies by legislation](https://webgate.ec.europa.eu/single-market-compliance-space/notified-bodies/by-legislation?ref=sorena.io) - Official EU directory source for finding notified bodies by legislation, including Regulation (EU) 2023/1230 on machinery.

*Recommended next step*

*Placement: after records section*

## Review a machinery modification before release

Use the substantial modification record to decide whether the change stays in maintenance controls or needs a manufacturer-level conformity file for the affected machinery or related product.

- [Open Research Copilot](/solutions/research-copilot.md): Answer Machinery Regulation scope and evidence questions with cited outputs.
- [Talk through implementation](/contact.md): Review the modification facts, risk assessment, conformity route, and records.

## Records to keep after the decision

The record should let a reviewer reconstruct the decision without knowing the project history. Keep both the threshold analysis and the resulting conformity work, including any conclusion that the change was not substantial.

For a substantial modification, retain the updated technical documentation and EU declaration of conformity for the required period and keep the release evidence aligned with the modified product identity. Where an assembly is only partly affected, keep the rationale for excluding unaffected machinery or related products from repeated tests or new documentation.

- Change record: product identity, baseline configuration, modification description, implementer, affected boundary, and whether the change was foreseen or planned.
- Threshold record: new hazards, increased risks, control-system impacts, stability or mechanical-strength impacts, protective measures, and final substantial-modification decision.
- Risk file: hazard identification, risk estimation, risk evaluation, risk reduction, verification, residual-risk decisions, and EHSR matrix.
- Technical documentation index: drawings, calculations, control-system records, software or programming-logic references, standards or common specifications, test reports, inspections, instructions, and safety information.
- Release file: conformity assessment route, notified-body evidence where applicable, EU declaration of conformity, CE-marking evidence, release approval, and authority-response log.

Sources for this answer:

- [Regulation (EU) 2023/1230 on machinery](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A02023R1230-20230629&ref=sorena.io) - Grounds technical-documentation and EU declaration retention, plus Article 18 treatment of affected and unaffected parts of an assembly.
- [ISO 12100:2010 - Safety of machinery](https://www.iso.org/obp/ui/en/?ref=sorena.io#!iso:std:51528:en) - Supports documenting and verifying the risk assessment and risk-reduction process.

## Primary sources

- [Regulation (EU) 2023/1230 on machinery](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A02023R1230-20230629&ref=sorena.io) - Primary legal source for the substantial modification definition, Article 18 manufacturer treatment, Article 10 manufacturer obligations, Article 25 conformity assessment, EU declaration of conformity, CE marking, and evidence retention.
  - Quote: "substantial modification"
- [EUR-Lex summary - machinery safety requirements](https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=LEGISSUM%3A4804067&ref=sorena.io) - Official summary used for the EHSR, conformity-assessment, EU declaration of conformity, CE-marking, instructions, and safety information overview.
  - Quote: "Conformity assessment procedures"
- [European Commission machinery sector page](https://single-market-economy.ec.europa.eu/sectors/mechanical-engineering/machinery_en?ref=sorena.io) - Commission machinery context for substantial modification as de facto new machinery and for machinery legislation implementation resources.
  - Quote: "de facto new machinery"
- [ISO 12100:2010 - Safety of machinery](https://www.iso.org/obp/ui/en/?ref=sorena.io#!iso:std:51528:en) - Machinery-safety standard grounding for hazard identification, risk assessment, risk reduction, documentation, and verification concepts.
  - Quote: "risk assessment and risk reduction"
- [Single Market Compliance Space - notified bodies by legislation](https://webgate.ec.europa.eu/single-market-compliance-space/notified-bodies/by-legislation?ref=sorena.io) - Official EU directory source for finding notified bodies for conformity assessment activities by legislation.
  - Quote: "conformity assessments"

## Related Topic Guides

- [Declaration of Conformity vs Declaration of Incorporation | Machinery Regulation FAQ](/artifacts/eu/machinery-regulation/faq/doc-and-doi.md): FAQ on when machinery needs an EU Declaration of Conformity and when partly completed machinery needs an EU Declaration of Incorporation under Regulation (EU) 2023/1230.
- [Directive 2006/42/EC to Machinery Regulation transition](/artifacts/eu/machinery-regulation/transition-from-directive-2006-42-ec.md): Transition guide for moving EU machinery files from Directive 2006/42/EC to Regulation (EU) 2023/1230, focused on the 20 January 2027 changeover, pipeline products, declarations, standards, technical documentation, software, cybersecurity, and digital instructions.
- [EU Machinery Regulation Applicability Test](/artifacts/eu/machinery-regulation/applicability-test.md): Test whether a product is machinery, a related product, partly completed machinery, a safety component, substantially modified, excluded, or covered by overlapping EU product laws.
- [EU Machinery Regulation compliance](/artifacts/eu/machinery-regulation/compliance.md): Machinery Regulation compliance checklist covering scope, EHSR risk assessment, technical documentation, instructions, conformity assessment, EU declarations, CE marking, software, transition, and market surveillance.
- [EU Machinery Regulation compliance checklist](/artifacts/eu/machinery-regulation/checklist.md): Checklist for Regulation (EU) 2023/1230 covering scope, EHSR risk assessment, technical documentation, instructions, conformity assessment, EU declarations, CE marking, digital duties, transition, and market surveillance.
- [EU Machinery Regulation deadlines and compliance calendar](/artifacts/eu/machinery-regulation/deadlines-and-compliance-calendar.md): Calendar for Regulation (EU) 2023/1230 dates, Directive 2006/42/EC transition, release documentation gates, standards monitoring, and substantial-modification reviews.
- [EU Machinery Regulation FAQ](/artifacts/eu/machinery-regulation/faq.md): Answers to Machinery Regulation questions on scope, partly completed machinery, Annex I categories, Article 25 conformity assessment, digital instructions, software, cybersecurity, transition, CE files, and overlap with other EU product laws.
- [EU Machinery Regulation Partly Completed Machinery](/artifacts/eu/machinery-regulation/partly-completed-machinery.md): What counts as partly completed machinery under Regulation (EU) 2023/1230, what documents travel with it, and where the final assembler takes over.
- [EU Machinery Regulation requirements](/artifacts/eu/machinery-regulation/requirements.md): Requirements under Regulation (EU) 2023/1230: machinery scope, EHSR risk assessment, technical documentation, instructions, conformity assessment, EU declaration, CE marking, software evidence, transition, and surveillance.
- [EU Machinery Regulation Safety Components](/artifacts/eu/machinery-regulation/safety-components.md): Definition, scope, conformity assessment, technical documentation, declaration, CE marking, and grounded examples for safety components under Regulation (EU) 2023/1230.
- [EU Machinery Regulation scope and machine categories](/artifacts/eu/machinery-regulation/scope-and-machine-categories.md): Scope guide for Regulation (EU) 2023/1230 covering machinery, related products, partly completed machinery, Annex I categories, exclusions, substantial modification, and category evidence.
- [EU Machinery Regulation substantial modification decision workflow](/artifacts/eu/machinery-regulation/substantial-modification-workflow.md): Workflow for assessing substantial modification under Regulation (EU) 2023/1230: change facts, hazard and risk impact, manufacturer obligations, conformity assessment, CE marking, and evidence.
- [EU Machinery Regulation vs LVD](/artifacts/eu/machinery-regulation/machinery-vs-lvd.md): Compare the EU Machinery Regulation and Low Voltage Directive boundary for machinery EHSRs, electrical risks, excluded electrical products, CE documentation, and evidence reuse.
- [EU Machinery Regulation vs Market Surveillance Regulation: compliance comparison](/artifacts/eu/machinery-regulation/machinery-vs-msr.md): Compare Machinery Regulation product compliance duties with EU MSR market surveillance duties, authority requests, online sales, corrective action and evidence records.
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- [EU Machinery Risk Assessment Method](/artifacts/eu/machinery-regulation/risk-assessment-method.md): How to document an EU Machinery Regulation risk assessment: ISO 12100 hazard identification, EHSR mapping, risk reduction, residual risk, software, cybersecurity, and technical-file evidence.
- [How to map Annex III EHSRs under the EU Machinery Regulation | Machinery Regulation FAQ](/artifacts/eu/machinery-regulation/faq/annex-iii-ehsr.md): FAQ on mapping Annex III essential health and safety requirements to hazards, risk reduction, software controls, technical documentation, and Annex I classification under Regulation (EU) 2023/1230.
- [Machinery CE documentation template for Regulation (EU) 2023/1230](/artifacts/eu/machinery-regulation/machinery-ce-documentation-template.md): Template fields for Machinery Regulation CE documentation: product identity, scope, EHSR risk assessment, standards, tests, instructions, EU declaration, CE marking, notified body route, software, cyber, and substantial modification checks.
- [Machinery Regulation and EU AI Act overlap for AI-enabled safety functions](/artifacts/eu/machinery-regulation/faq/ai-act-overlap.md): FAQ on Machinery Regulation overlap with the EU AI Act for self-evolving or machine-learning safety functions, Annex I categories, standards work, and technical documentation boundaries.
- [Machinery Regulation Annex I conformity route workflow](/artifacts/eu/machinery-regulation/annex-i-route-workflow.md): Classify machinery against Annex I Part A and Part B, choose the Article 25 conformity assessment route, and assemble the technical evidence file.
- [Machinery Regulation Annex I high-risk categories](/artifacts/eu/machinery-regulation/annex-i-and-high-risk-machinery.md): Explain what Annex I does under Regulation (EU) 2023/1230, which listed machinery categories trigger special conformity routes, and what evidence to keep.
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