Employers with 100 or more employees (or government contractors of $50,000 or more with 50 or more employees) are required to file an Employer Information Report (EEO-1) each year on Sept. 30 with the EEOC’s EEO-1 Joint Reporting Committee. The EEO-1 report includes data on protected class representation in various job categories. 

Filing is generally done through the Equal Employment Opportunity Commission’s Web site.
The EEOC and Office of Federal Contract Compliance Programs (OFCCP) utilize the form to look for potential under-representation and to take any necessary investigatory/remedial action.
Penalties for noncompliance can be severe, including a ban on future government contracts and large fines.