An "official complaint" is a formal statement made by someone to report their dissatisfaction or grievance regarding a specific issue or problem to the relevant authority or organization. Full definition
Unfortunately, members of small associations are particularly reluctant to file official complaints because, even though ethics proceedings are confidential, not much in a small town is secret. (nar.realtor)
He went as far as making official complaints that were flat out rejected. (zillow.com)
Unfortunately, there is no centralized place where official complaints against adoption agencies will be found, so you have to check a few different places. (creatingafamily.org)