Practice 3 minutes read

The impact assessment: when it becomes mandatory

Where a high risk is likely, Article 35 GDPR requires an impact assessment before processing begins. The threshold is lower than many assume – and the timing is the real sticking point.

The impact assessment is not a review after the fact but a planning tool. It is meant to surface risks while the project can still be changed – which is precisely why it has to exist before processing starts, not after the first complaint.

When it is mandatory

Article 35(3) names three cases where it is always required: extensive evaluation of personal aspects by automated processing, extensive processing of special categories of data, and systematic extensive monitoring of publicly accessible areas.

Alongside that, every supervisory authority maintains its own list of processing operations for which an assessment is compulsory. These lists are published and are the quickest way into the question.

The Board's rule of thumb

Do two or more of the nine risk criteria apply to the project?
Yes – two or moreAn impact assessment is as a rule required, and it has to happen before processing begins.
No – at most oneUsually dispensable. The assessment of that question still belongs on record – a dated note with reasons is enough.
The nine criteria: evaluation and scoring, automated decisions with significant effects, systematic monitoring, special categories of data, large-scale processing, matching or combining datasets, vulnerable data subjects, innovative technology, and processing that prevents people from exercising a right.

What belongs in the document

  1. A description of the planned processing: purposes, kinds of data, people affected, recipients, periods, technology used.
  2. An assessment of necessity and proportionality – can the purpose be reached with less data?
  3. The risks to rights and freedoms – from the perspective of the people affected, not of the company.
  4. The measures planned to address them and the residual risk once they are in place.

When the residual risk stays high

If a high risk remains after all planned measures, Article 36 requires prior consultation with the supervisory authority. It has eight weeks to respond, extendable by a further six. Processing may not begin until then.

In practice such consultations are rare – not because high residual risks are rare, but because a project is as a rule adjusted once the assessment makes the risk visible. That is exactly its purpose.

An impact assessment concluding that everything is fine was either unnecessary or came too late.

Published 21 September 2026

This article explains general principles and does not replace legal advice on an individual case.

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