The legitimate interests assessment (LIA) template is designed to help you to decide whether or not the legitimate interests basis is likely to apply to your processing. It should be used alongside the UK's ICO guidance available here: https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/lawful-basis/a-guide-to-lawful-basis/lawful-basis-for-processing/legitimate-interests/
Purpose test
The purpose test identifies the reason for the processing of personal data and helps you determine if it meets the criteria for legitimate interest. You should consider why you want to process the data, what benefits the processing will yield and to whom, and if there are regulatory or ethical issues with the processing.
Necessity test
Once a purpose has been identified, you should consider whether the processing contemplated is necessary to achieve it. You should weigh if there might be other ways to realize the purpose without processing personal information or by processing less data.
Balancing test
Next, you should weigh the impact the processing would have on individuals’ rights and freedoms and assess whether this overrides your legitimate interests. Consider the types of data processed (e.g., special category, criminal offense, or children’s data), whether the data subjects would reasonably expect that their information would be used in such a way, and the likely impact to them.
Decision-making
Finally, you should document the outcome of the assessment in the decision-making section.