To file a complaint online, select the topic below "What's the reason for your inquiry?" on the USPS "Email us" page. File an Online Complaint.Fill out the entire form and provide as much information as possible. 4. This online complaint form will be utilized for investigatory purposes so it is important to fill out each field and provide as much information as possible. COMPLAINANT (person filing the complaint). NAME. Whistleblower Complaint Form. Report Fraud, Waste, and Abuse. Thief complaint form. Once a password reset link is sent via email it requires receiving a text message for verification. Please take a few minutes to fill out a brief survey, available in English and Spanish.