Which type of complaint requires documentation of actions taken?

The correct choice is formal complaint, as this type necessitates a systematic documentation of the issues raised and the actions that have been taken to address them. A formal complaint follows an established process that typically includes recording specific details, such as the nature of the complaint, the individuals involved, and the steps taken to resolve the issue. This documentation serves multiple purposes: it provides a clear record for future reference, helps ensure accountability, and is often required for institutional procedures or legal processes.

In contrast, informal complaints may not require such detailed documentation. They often involve a more straightforward conversational exchange where issues are raised and addressed without the need for formal records. This allows for a more flexible and immediate response. Therefore, it is in the nature of formal complaints that they require comprehensive records to facilitate appropriate resolution processes.