A basis on which you can legally motivate your processing
. There are six available legal basis under the GDPR
- performance of a Contract (including taking steps to conclude a contract)
- Legal obligation
- Vital interest of the data subject or another individual
- Task of public interest
- Legitimate interest of the data controller
Which one that is the most appropriate depends on the context of your processing.
Note that public authorities most often cannot rely legitimate interest as a legal basis.