Data Minimisation
The principle that only personal data that is adequate, relevant, and limited to what is necessary should be collected and processed.
Full Definition
Data Minimisation is a core data protection principle requiring organisations to collect and process only the personal data that is strictly necessary for the specified, explicit, and legitimate purpose. It involves limiting collection (not gathering data 'just in case'), restricting access (only those who need the data should have it), and applying retention limits (deleting data once the purpose is fulfilled). Practically, this means designing forms to ask only for essential fields, avoiding unnecessary data replication, and conducting regular data audits to identify and delete stale personal data.
How each law treats it
Personal data must be adequate, relevant and limited to what is necessary. Minimisation is a principle, not a quantitative rule — the regulator looks at necessity for the stated purpose.
Collection must be for the specified purpose and no more. Retention beyond the purpose is a separate violation of Section 9.
Data minimisation was introduced by the CPRA — collection, use, retention and sharing must be reasonably necessary and proportionate.
In practice
- Trigger a necessity review for every form field, API parameter and database column that captures personal data.
- Default to the shortest viable retention period and extend only when a specific legal, contractual or legitimate-interest need is documented.
- Design minimisation into the collection path — a field that doesn't exist is one you don't have to delete later.
Common pitfalls
- Collecting data because it 'might be useful later' — the GDPR Article 5 principle forecloses this exact pattern.
- Retaining raw logs long after the operational need has passed because deletion scripts are complicated to write.
- Treating minimisation as an engineering problem; it's a product-design problem that engineering supports.
Frequently asked questions
Is anonymised retention compatible with data minimisation?+
Yes, provided the anonymisation is irreversible. The GDPR explicitly supports anonymisation as a route to retain analytical value without retaining personal data.
How do I justify retaining a copy for 'legal defence'?+
A specific limitation period (statute of limitations) plus a documented legitimate-interests balancing test. 'In case we get sued' is not justification on its own; name the specific legal exposure and the applicable limitation period.
What's the GDPR evidence for a minimisation decision?+
A documented purpose definition + a necessity analysis per field. The RoPA is where you keep it; the DPA auditor will ask for the analysis if the field looks surplus.
Related terms
Relevant regulations
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