DefinitionIn forcev1.0.0

Substantial modification

A change to an AI system after it has been placed on the market or put into service that the provider did not foresee in the initial conformity assessment, and that affects compliance with Chapter III, Section 2 or changes the intended purpose.

The official source remains authoritative. This is general information about obligations and not legal advice. See this object on the map

Address and citation

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Identifier: praxikon:eu:ai-act:definition:definitie-substantiele-wijziging
Payload hash (sha256): 1695d1dc88c1730de688ee4975230bf449ed94ea90a06e6ce04434b17759537d

Citation line

Praxikon, "Substantial modification", praxikon:eu:ai-act:definition:definitie-substantiele-wijziging@1.0.0, dataset praxikon:sys:registry:dataset:ai-act-implementation-graph 2.1.0 (schema 1.4.0), effective_at 2026-08-08T00:00:00.000Z, known_at 2026-08-14T00:00:00.000Z, sha256 1695d1dc88c1730de688ee4975230bf449ed94ea90a06e6ce04434b17759537d

Version: 1.0.0
Legal time (effective_at): 8 August 2026
Knowledge time (known_at): 8 August 2026
Closed on: Not closed
Application date: 1 August 2024
Topics: definitions

Review status: Placed against the official source (8 August 2026). Next check due by 4 February 2027. The check date is the knowledge date of this version; no later recheck has been recorded.

What this object links to

Every relation appears below as a path: from the source with its locator, through the conditions and exceptions of the object carrying the relation, to the consequence. A locator belongs to a statement in the data and not to a relation, so the source is the source anchor of the carrying object.

What this object is about

2 of 2 shown

The object is about this role. Undifferentiated: it does not follow that the duty rests on this role.

Source
Official fact on this object, with its locator.
- EU Artificial Intelligence Act 2024/1689
  Locator: Article 3(23)
  praxikon:eu:ai-act:source:reg-eu-2024-1689
  Open official source
Via
No condition or exception recorded on this object.
Consequence
- ActorDeployer
  praxikon:eu:ai-act:actor:deployer
- ActorProvider of an AI system
  praxikon:eu:ai-act:actor:provider

What this object states

Official fact

Attributable to a named primary source, with a locator. Where they differ, the official source prevails.

Article 3(23) defines substantial modification as a change to an AI system after its placing on the market or putting into service which was not foreseen or planned by the provider in the initial conformity assessment and as a result of which compliance with the requirements set out in Chapter III, Section 2 is affected, or which results in a modification of the intended purpose for which the AI system was assessed.
- Locator: Article 3(23)praxikon:eu:ai-act:source:reg-eu-2024-1689Open official source

Our interpretation

Our own reading. It can change without the law changing, and it is not the position of a supervisory authority.

This definition decides when you must reassess, and it contains an escape route that is often missed: changes the provider foresaw and planned in the conformity assessment are not substantial modifications. A system that keeps learning within predefined boundaries therefore falls outside it in principle, while a model you retrain on a new population or repurpose does not. Note also the link with Article 25: if you change the intended purpose, you as deployer can become the provider. The legal term is substantial modification, not material change.
- Locator: Article 3(23)praxikon:eu:ai-act:source:reg-eu-2024-1689Open official source

Recommended step

A practical step we consider appropriate. Not an obligation following from the Regulation.

Keep a change log per AI system with the date, nature of the change, the reason, and the assessment of whether it is a substantial modification, including who determined that. Agree with your provider in advance which changes were already foreseen in the conformity assessment, so you do not have to argue afterwards about whether reassessment was required.
- Locator: Article 3(23)praxikon:eu:ai-act:source:reg-eu-2024-1689Open official source

When this applies

No condition recorded on this object.

When this does not apply

No exception recorded on this object.

Referring to this object

Citation block

Copy this reference into your advice, article or file. The identifier, the version and the hash keep the statement findable later, even once the dataset has moved on.

Reference

Praxikon, "Substantial modification",
praxikon:eu:ai-act:definition:definitie-substantiele-wijziging@1.0.0,
dataset praxikon:sys:registry:dataset:ai-act-implementation-graph 2.1.0 (schema 1.4.0),
effective_at 2026-08-08T00:00:00.000Z, known_at 2026-08-08T00:00:00.000Z,
sha256 1695d1dc88c1730de688ee4975230bf449ed94ea90a06e6ce04434b17759537d,
https://www.praxikon.com/en/verkenner/definition/definitie-substantiele-wijziging
(https://www.praxikon.com/api/v1/entities?id=praxikon%3Aeu%3Aai-act%3Adefinition%3Adefinitie-substantiele-wijziging&effective_at=2026-08-08&known_at=2026-08-08&lang=en, accessed 2026-08-23)

Short form

praxikon:eu:ai-act:definition:definitie-substantiele-wijziging@1.0.0 (sha256 1695d1dc)

BibTeX

@misc{praxikon-eu-ai-act-definition-definitie-substantiele-wijziging-1-0-0,
  author       = {{Praxikon}},
  title        = {Substantial modification},
  year         = {2026},
  version      = {1.0.0},
  number       = {praxikon:eu:ai-act:definition:definitie-substantiele-wijziging},
  howpublished = {AI Act Change \& Evidence Graph, dataset 2.1.0, schema 1.4.0},
  note         = {effective_at 2026-08-08T00:00:00.000Z; known_at 2026-08-08T00:00:00.000Z; sha256 1695d1dc88c1730de688ee4975230bf449ed94ea90a06e6ce04434b17759537d},
  url          = {https://www.praxikon.com/en/verkenner/definition/definitie-substantiele-wijziging},
  urldate      = {2026-08-23},
  language     = {en}
}

CSL JSON

[
  {
    "id": "praxikon:eu:ai-act:definition:definitie-substantiele-wijziging@1.0.0",
    "type": "dataset",
    "title": "Substantial modification",
    "container-title": "AI Act Change & Evidence Graph",
    "publisher": "Praxikon",
    "version": "1.0.0",
    "number": "praxikon:eu:ai-act:definition:definitie-substantiele-wijziging",
    "URL": "https://www.praxikon.com/en/verkenner/definition/definitie-substantiele-wijziging",
    "language": "en",
    "issued": {
      "date-parts": [
        [
          2026,
          8,
          8
        ]
      ]
    },
    "accessed": {
      "date-parts": [
        [
          2026,
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        ]
      ]
    },
    "note": "dataset praxikon:sys:registry:dataset:ai-act-implementation-graph 2.1.0; schema 1.4.0; effective_at 2026-08-08T00:00:00.000Z; known_at 2026-08-08T00:00:00.000Z; sha256 1695d1dc88c1730de688ee4975230bf449ed94ea90a06e6ce04434b17759537d; retrieved_from https://www.praxikon.com/api/v1/entities?id=praxikon%3Aeu%3Aai-act%3Adefinition%3Adefinitie-substantiele-wijziging&effective_at=2026-08-08&known_at=2026-08-08&lang=en; licence https://www.praxikon.com/nl/legal/terms"
  }
]

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