Some people have come to usa from different parts of the globe on visiting visa. After they have come here, some are getting contract marriages by paing some money in order to get immigration/green card. Even they are creating false bank statements, false rental agreements etc. though they are not staying together. Out of them are even not paying income tax too, either to the federal govt. and or to the state governments. I know they are working too. I know some employers have given job to them too.
Whom I have to report please ? Its about question of immigration law and question of IRS law violation.

I am pretty sure you can start by reporting it to the Police or criminal stoppers along with enough evidence of course.