There is no single "master list" that a citizen can check online to see if their passport is flagged, as much of this data is restricted for security and law enforcement reasons. However, you can infer or check your status through specific channels. If you are concerned about a "travel ban," you can visit the official immigration portal of the country you intend to visit; some countries, like the UAE or India, have specific e-services where you can enter your passport number to check for active "circulars" or legal restrictions. In the United States, if you consistently face "Secondary Inspection" or find "SSSS" on your boarding pass, your name may be on a watch list; you can resolve this by applying for a Redress Control Number through the DHS Traveler Redress Inquiry Program (DHS TRIP). For general validity or "flagging" due to lost/stolen reports, you can contact your local passport issuing office or use their official tracking portal (like Passport Seva in India) to check the current status of your document and see if it is marked as active or suspended.