How can I force administrator to provide a reason when cancelling a user account
In User fields, add field of type: List Text with checkboxes radio button as widget
Use the Filed Permissions module so only admins can see this user field.
Download Rules and enable Rules UI
Create a New Rule
React on: After Updating an Existing User Account
Add Condition: Data Comparison &gt;&gt; account-unchanged:status &gt;&gt; Operator: Equals DATA Value: Blocked
Add Action &gt;&gt; Send Mail &gt;&gt; Body: [user:name] was blocked because [user:field-example]