Contact your local immigration enforcement agency or national border agency
Use the official government tip line or online reporting form if available
Provide the person’s full name, address, workplace, and other identifying details if known
Include any relevant dates, times, locations, and observed activities
Report only information you know to be true
Do not harass, threaten, or confront the person
If there is an immediate danger or crime in progress, call emergency services
If you are unsure which agency to contact, check your country’s official government website