Where to report false marriage just for paperwork- INS?

If you suspect a marriage has been entered into solely for Immigration purposes, you can report it to the U.S. Citizenship and Immigration Services (USCIS) or the Department of Homeland Security (DHS). You can submit your concerns through the USCIS Tip Form available on their website or contact the Immigration Fraud Tip Line. It's important to provide as much information as possible to assist in the investigation.