---
title: "EU Machinery Regulation substantial modification decision workflow"
canonical_url: "https://www.sorena.io/artifacts/eu/machinery-regulation/substantial-modification-workflow"
source_url: "https://www.sorena.io/artifacts/eu/machinery-regulation/substantial-modification-workflow"
author: "Sorena AI"
description: "Workflow for assessing substantial modification under Regulation (EU) 2023/1230: change facts, hazard and risk impact, manufacturer obligations, conformity assessment, CE marking, and evidence."
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 substantial modification decision workflow

Workflow for assessing substantial modification under Regulation (EU) 2023/1230: change facts, hazard and risk impact, manufacturer obligations, conformity assessment, CE marking, and evidence.

*Workflow* *EU*

## EU Machinery Regulation substantial modification workflow

Use this workflow when a physical or digital change may affect the safety of machinery or a related product after it has been placed on the market or put into service.

The goal is to decide whether the change is a substantial modification, whether the modifier is treated as the manufacturer, and which risk, technical-documentation, conformity-assessment, declaration, CE-marking, and evidence steps must be completed.

A substantial modification assessment should start with the actual change, not with a generic compliance checklist. Capture what changed, test it against the Machinery Regulation definition, decide whether the modifier takes manufacturer obligations for the affected machinery or related product, and keep the risk and conformity evidence that supports the decision.

## 1. Identify the modification before judging it

Open the file with a change record that shows the product model, serial or configuration range, market status, and whether the change is physical, digital, or both. The definition applies after machinery or a related product has been placed on the market or put into service, so the record should distinguish a post-market or in-service change from ordinary design work before first release.

Describe who will carry out the change, whether the original manufacturer foresaw or planned it, and whether the change affects the whole machine, a related product, or only a part of an assembly of machinery. That scope matters because Article 18 ties the modifier's manufacturer obligations to the machinery or related product affected by the substantial modification, as demonstrated in the risk assessment.

- Record the modification type: mechanical, electrical, control-system, software, firmware, safety-function, guard, protective-device, stability, load, speed, operating-mode, or operating-environment change.
- Record the baseline: original instructions, intended use, limits of use, existing safeguards, applicable EHSRs, standards or common specifications used, EU declaration of conformity, and technical documentation reference.
- Record the affected boundary: whole product, related product, partly affected assembly, safety component, control system, guard, protective device, or stability/mechanical-strength element.
- Record whether the change was foreseen or planned by the manufacturer; if it was not, move to the hazard and risk impact test.

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) - Defines substantial modification as a physical or digital change after placing on the market or putting into service, and Article 18 ties the modifier's duties to the affected machinery or related product.
- [European Commission machinery sector page](https://single-market-economy.ec.europa.eu/sectors/mechanical-engineering/machinery_en?ref=sorena.io) - Commission sector context explains that existing machinery can be modified to such an extent that it becomes de facto new machinery.

## 2. Test whether the change creates a substantial modification

Apply the substantial modification definition as a threshold test. A change should be treated as substantial only when the change was not foreseen or planned by the manufacturer, affects safety by creating a new hazard or increasing an existing risk, and requires one of the protective responses named in the Regulation.

Do not treat every service activity as substantial. The Regulation's recitals distinguish repair and maintenance operations that do not affect compliance with the relevant essential health and safety requirements from substantial modifications.

- Hazard trigger: identify each new hazard introduced by the modification, including hazards from software, control logic, changed use, new access points, changed energy, changed loads, or changed interaction with operators.
- Risk trigger: identify each existing risk whose severity, probability, exposure, avoidance, stability margin, mechanical strength, or control reliability materially increases.
- Protective-measure trigger: check whether the change requires adding guards or protective devices whose processing requires modifying the existing safety control system.
- Stability or strength trigger: check whether additional protective measures are needed to ensure stability or mechanical strength.
- Non-substantial outcome: if the change is repair or maintenance and the evidence shows no effect on compliance with relevant EHSRs, record that rationale and keep the evidence with the service file.

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) supplies the substantial-modification elements: not foreseen or planned, safety affected, new hazard or increased risk, and specified protective measures.
- [ISO 12100:2010 - Safety of machinery](https://www.iso.org/obp/ui/en/?ref=sorena.io#!iso:std:51528:en) - ISO 12100 grounding supports a structured hazard-identification, risk-estimation, risk-evaluation, risk-reduction, documentation, and verification approach for machinery safety work.

## 3. If substantial, treat the modifier as the manufacturer for the affected scope

When the threshold is met, Article 18 treats the natural or legal person carrying out the substantial modification as the manufacturer for the machinery or related product concerned. If only part of an assembly is affected, the scope can be limited to the affected machinery or related product, but the risk assessment must demonstrate that boundary.

The modifier should then stop treating the activity as a maintenance closeout and run the manufacturer-obligation workstream for the affected scope. That includes ensuring conformity with applicable requirements, applying the relevant conformity assessment procedure, and declaring conformity on its own responsibility.

- Name the Article 18 responsible person or legal entity and the affected machinery or related product.
- Update the risk assessment to show the modified hazards, increased risks, protective measures, and any unaffected parts of an assembly.
- Map applicable EHSRs from Annex III to the modified design, construction, safeguards, control functions, instructions, and safety information.
- Decide whether other Union harmonisation legislation covers some risks more specifically, because the Machinery Regulation does not apply to those risks to the extent that the specific legislation covers them.

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 states that the person carrying out a substantial modification is considered the manufacturer and must apply manufacturer obligations for the affected machinery or related product.

## 4. Rebuild the conformity file before release or use

For a substantial modification, the evidence file should be rebuilt around the modified scope. Article 10 requires the manufacturer to ensure design and construction against Annex III EHSRs, draw up technical documentation, carry out or have carried out the relevant conformity assessment, then draw up the EU declaration of conformity and affix the CE marking after conformity has been demonstrated.

Select the conformity assessment route under Article 25 for the affected machinery or related product. Annex I Part A categories require the specified procedures involving a notified body route; Annex I Part B allows internal production control only when the machinery or related product was designed and constructed according to the relevant harmonised standards or common specifications covering all relevant EHSRs; products not listed in Annex I use internal production control.

- Risk assessment: update hazard identification, risk estimation, risk evaluation, risk reduction, verification, and the affected-scope boundary.
- EHSR matrix: mark each Annex III requirement as applicable, not applicable with rationale, met by design, met by protective measure, met by information, or requiring open action.
- Technical documentation: update drawings, calculations, control logic, software or programming-logic references where relevant, test reports, standards or common specifications, instructions, and verification records.
- Conformity assessment: document the Article 25 route, notified body involvement where required, certificates or approvals where applicable, and why the selected route fits the modified product category.
- Declaration and CE marking: issue or update the EU declaration of conformity for the modified machinery or related product and affix CE marking only after conformity 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) - Articles 10 and 25 ground the manufacturer workstream: EHSRs, technical documentation, conformity assessment, EU declaration of conformity, and CE marking.
- [Single Market Compliance Space - notified bodies by legislation](https://webgate.ec.europa.eu/single-market-compliance-space/notified-bodies/by-legislation?ref=sorena.io) - Grounds where teams can check notified bodies for conformity assessments under listed EU legislation, including machinery entries.

*Recommended next step*

*Placement: after evidence section*

## Turn the modification decision into an evidence file

Use the workflow to record the change, hazard and risk impact, affected scope, conformity route, declaration, CE-marking status, and release evidence for the modified machinery or related product.

- [Open Research Copilot](/solutions/research-copilot.md): Check Machinery Regulation scope, evidence, and conformity-assessment questions with cited outputs.
- [Talk through implementation](/contact.md): Review your modification facts, risk assessment, EHSR matrix, technical documentation, and release evidence.

## 5. Keep the substantial modification evidence pack

Close the workflow only when the file explains both the decision and the release state. The evidence should let a reviewer see why the change was or was not substantial, what hazards or risks changed, which product boundary was affected, and which conformity work was completed before the modified machinery or related product was placed on the market or put into service.

For substantial modifications, keep the updated technical documentation and EU declaration of conformity available for market-surveillance authorities for the required retention period. Keep unaffected-assembly evidence too, because the Regulation allows avoiding repeated tests and new documentation for machinery or related products in an assembly that are not affected by the modification.

- Change record with product identity, baseline configuration, modification description, implementer, affected boundary, and whether the change was foreseen or planned.
- Substantial-modification test showing new hazards, increased risks, guards or protective devices affecting safety controls, stability or mechanical-strength measures, and the final threshold decision.
- Risk assessment and EHSR matrix for the affected machinery or related product, including rationale for any assembly parts treated as unaffected.
- Technical documentation index with drawings, calculations, control-system and software records, standards or common specifications, test and inspection evidence, instructions, and safety information.
- Conformity assessment record, notified body correspondence or certificates 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 retention of technical documentation and EU declaration of conformity, plus the recital that unaffected assembly parts should not require repeated tests or new documentation.
- [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 in the evidence pack.

## 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"
- [European Commission machinery sector page](https://single-market-economy.ec.europa.eu/sectors/mechanical-engineering/machinery_en?ref=sorena.io) - Commission context for machinery legislation, substantial modification as de facto new machinery under the earlier machinery framework, notified bodies, CE marking, and sector guidance.
  - 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 used in the workflow.
  - 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 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 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.
- [EU Machinery Regulation: autonomous mobile and collaborative machinery](/artifacts/eu/machinery-regulation/autonomous-mobile-and-collaborative-machinery.md): Grounded guide to Regulation (EU) 2023/1230 requirements for autonomous mobile machinery, human-machine interaction, controls, software, cybersecurity, risk assessment, technical documentation, and conformity routes.
- [EU Machinery Regulation: when does a modification constitute substantial modification?](/artifacts/eu/machinery-regulation/substantial-modification.md): Guide to substantial modification under Regulation (EU) 2023/1230: change triggers, risk assessment, EHSRs, technical documentation, conformity assessment, CE marking, and records.
- [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.
- [Machinery Regulation category and scope checks](/artifacts/eu/machinery-regulation/category-and-scope-workflow.md): Check whether a product is machinery, a related product, partly completed machinery, a safety component, excluded from scope, or listed in Annex I under Regulation (EU) 2023/1230.
- [Machinery Regulation conformity assessment and CE marking](/artifacts/eu/machinery-regulation/conformity-assessment-and-ce.md): EU Machinery Regulation guide to Article 25 conformity assessment routes, Annex I machinery categories, technical documentation, EU declarations, CE marking, and instructions.
- [Machinery Regulation cybersecurity evidence FAQ](/artifacts/eu/machinery-regulation/faq/cybersecurity.md): What cybersecurity evidence connected or software-enabled machinery should keep for protection against corruption, safety-related control systems, and machinery risk assessment.
- [Machinery Regulation digital instructions](/artifacts/eu/machinery-regulation/digital-instructions.md): EU Machinery Regulation guide to digital instructions for use: access marking, print and download access, paper copies, non-professional safety information, languages, and records.
- [Machinery Regulation penalties and enforcement](/artifacts/eu/machinery-regulation/penalties-and-fines.md): EU Machinery Regulation enforcement guide covering Member State penalty rules, corrective action, market surveillance powers, and cross-border authority cooperation.
- [Machinery Regulation related products scope guide](/artifacts/eu/machinery-regulation/related-products.md): Classify EU Machinery Regulation related products, including interchangeable equipment, safety components, lifting accessories, lifting chains, ropes, webbing, and removable transmission devices.
- [Machinery Regulation software and cybersecurity considerations](/artifacts/eu/machinery-regulation/software-and-cybersecurity-considerations.md): How Regulation (EU) 2023/1230 treats safety-related software, control systems, corruption protection, technical documentation, and cyber-safety risk evidence.
- [Machinery Regulation Technical Documentation and Technical File](/artifacts/eu/machinery-regulation/technical-documentation-and-technical-file.md): What to keep in the EU Machinery Regulation technical file: product identification, risk assessment, EHSR mapping, standards, tests, instructions, declarations, software evidence, retention, and notified-body records.
- [Machinery Regulation technical file acceptance workflow](/artifacts/eu/machinery-regulation/technical-file-acceptance-workflow.md): Release-gate workflow for accepting an EU Machinery Regulation technical file: scope, EHSR risk evidence, standards, tests, declarations, notified-body records, software, cyber, and signoff.
- [Machinery Regulation Timeline and Transition: practical guide](/artifacts/eu/machinery-regulation/timeline-and-transition.md): EU Machinery Regulation guide to Timeline and Transition with scope decisions, owner actions, evidence records, source-linked citations, and practical next steps.
- [Machinery Regulation vs EMC Directive](/artifacts/eu/machinery-regulation/machinery-vs-emc.md): Compare EU machinery safety duties with EMC duties for equipment, CE documentation, harmonised standards, declarations, and combined technical files.
- [Machinery Regulation vs EU AI Act: machinery safety overlap](/artifacts/eu/machinery-regulation/machinery-regulation-vs-eu-ai-act.md): A grounded comparison of the EU Machinery Regulation and EU AI Act for machinery with AI-enabled safety functions, software, cyber-safety and technical documentation overlap.
- [Machinery Regulation vs Machinery Directive](/artifacts/eu/machinery-regulation/machinery-regulation-vs-machinery-directive.md): Grounded comparison of Regulation (EU) 2023/1230 and Directive 2006/42/EC across legal form, timing, scope, digital instructions, cybersecurity, conformity assessment, documentation, and CE marking.
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- [When can a software update affect Machinery Regulation compliance?](/artifacts/eu/machinery-regulation/faq/software-updates.md): FAQ on when machinery software updates can trigger Machinery Regulation review, including safety functions, substantial modification, corruption protection, instructions, and CE technical-file evidence.
- [When does used or modified machinery need a new conformity assessment? | Machinery Regulation FAQ](/artifacts/eu/machinery-regulation/faq/used-and-modified-machinery.md): FAQ on used and modified machinery under Regulation (EU) 2023/1230, including substantial modification, first EU use, technical documentation, and market surveillance evidence.
- [When is a notified body needed under the EU Machinery Regulation?](/artifacts/eu/machinery-regulation/faq/notified-bodies.md): FAQ on when Machinery Regulation Annex I products need a notified body, how to find designated bodies, and what manufacturers still own.
- [Which Article 25 conformity assessment module applies? | EU Machinery Regulation FAQ](/artifacts/eu/machinery-regulation/faq/article-25-modules.md): FAQ on Article 25 of Regulation (EU) 2023/1230: Module A, Module B plus C, Module H, Module G, Annex I triggers, notified body involvement, and technical file evidence.


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