If a standard is set by the IRS governing employers, than you would report that particular company to the IRS. From there the IRS would investigate any wrong doings and punish and/or fine any guilty parties. If the IRS does not investigate the crime and it concerns a particluar indivdual contact the Better Business Bureau (BBB).
The Internal Revenue Service website has the proper procedures that you need to take to file these violations. If you go to the website there should be a number you can call or an address you can contact to report your violations efficiently.
You can report them directly to the IRS, although they will want more than just naked allegations. For criminal wrongdoing, you can report it to the FBI.
Contact the Internal Revenue Services nearest for the Whistleblower Office number. They will be able to point you to the right place as well as possibly getting compensated for the information.
If the problem you want to report involves wages, you might want to start with the Department of Labor. They would be the place to contact for any wage disputes.