Legitimate interests: getting the most from your data, lawfully
"Legitimate interests" is one of six lawful bases for processing personal data under GDPR, and the most flexible. Used well, it lets businesses process personal data confidently - not just as a fallback. Here's how to use it properly.
1. The three-part test
To rely on legitimate interests, you need:
i. a genuine business reason for the processing,
ii. proof it's actually needed, and
iii. confirmation it doesn't unfairly override people's privacy rights.
This isn't a coin toss, it's a structured assessment and getting it right from the start matters. Even direct marketing is recognised in GDPR as a legitimate interest.
2. Define your interest clearly
How you describe your interest matters, too narrow and you box yourself in later. Too vague, and it won't survive a challenge. Common interests include fraud prevention, security, marketing, product improvement, and group data-sharing. You can rely on more than one interest for the same activity, stacking valid reasons strengthens your position.
3. "Necessary" doesn't mean "Minimal"
Necessity doesn't mean using the least data possible, it means the processing genuinely helps achieve your goal. If combining transaction details, device data, and behaviour patterns makes fraud detection more accurate, that can be justified. The test is effectiveness, not minimalism. Write down what you'd lose without each data type.
4. Winning the balancing test
People's expectations matter - being upfront about your data use, and using it consistently with your relationship, puts you in a stronger position. So do safeguards: pseudonymising data, limiting access, stripping unnecessary detail. A company processing more data safely can be better off than one processing less data carelessly.
5. Reusing data you already hold
Article 6(4) of the GDPR lets you use data for a new purpose without fresh consent, if it's compatible with the original purpose. Check compatibility against the link between purposes, the context of collection, the data type, the consequences for the person, and the safeguards in place. This can unlock real value from data you already hold.
6. Profiling and automated decisions
You can profile customers, for marketing, personalisation, or risk scoring, under legitimate interests, subject to the balancing test. This is separate from the stricter rules on fully automated decisions with serious effects on someone. You can profile customers while ensuring a human stays meaningfully involved, with extra care where profiling touches sensitive data or vulnerable people.
7. The right to object
People can object to legitimate interests processing, and you must stop unless you can show compelling grounds, why a solid, documented assessment matters. For direct marketing, the right to object is absolute: no balancing, no exceptions.
In our experience, easy, genuine opt-outs is the key here, it also builds trust and helps strengthen your market position overall.
Conclusion
Legitimate interests is a serious tool, not a shortcut. Businesses that assess it properly, document their reasoning, build in safeguards, and communicate clearly will get real value from it - the ones that thrive aren't those avoiding scrutiny, but those that can stand up to it.
10 Key takeaways
1. Define your interest clearly and broadly.
2. Necessity means effective, not minimal.
3. Safeguards strengthen your position.
4. Transparency supports wider use of data.
5. Reuse data already held where compatible.
6. Profiling is allowed - keep it separate from automated-decision rules.
7. Document your reasoning in advance.
8. Always honour marketing opt-outs, no exceptions.
9. Keep records - they're your evidence base.
10. Lead with legitimate interests, not consent, where it fits.
Want to maximise the data in your business? We can help you assess your current personal data and put practical compliance measures in place, while still maximining its use. Get in touch with Privacy Path today for a free initial consultation.