1. One way to avoid eVerify is to keep your payroll under the minimum reporting requirements. In Tennessee, for example, there is no reporting requirement for companies with less than 35 employees. Then, payroll has to be handled in-house -- the payroll processors will require I-9s, and if they don't check out, they will flag them. Typically undocumented employees will provide fake credentials, including fake SSNs. Wages are withheld and credited to the actual owner of the SSN, who more often than not does not catch it. The employer, however, almost always is aware and turns a blind eye to the process, because the employer needs the workers. Lots of times the employer will create new companies to make sure that they can remain under the reporting requirements.
2. Pay wages in cash and don't withhold.
Both of these common methods of hiring undocumented workers are illegal.