When you hire a new employee, you must verify that the employee is legally authorized to work in the United States. This doesn't mean all employees must be U.S. citizens; permanent residents, those with work visas, and others may work here legally. However, you may not knowingly hire or recruit unauthorized aliens for employment, nor may you allow employees to continue working for you if they can't show proper documentation of their identity and their authorization to work in this country.
So how do you do the required checking? By completing USCIS Form I-9, Employment Eligibility Verification. (You can find copies of the form, along with lots of helpful information about it, at the USCIS I-9 Central page.
After you hire an employee, you have three business days to complete Form I-9. If you are hiring someone for less than three days total, you must complete Form I-9 before the end of the employee's first day of work.
You may complete only Section 3 of the form, "Reverification and Rehires," if you have already completed an original Form I-9 for that employee and:
First, the employee must complete the first section of the form by providing basic identification information, including name, address, and telephone number. The employee must also swear that he or she is authorized to work in the United States, including his or her status (citizen, legal permanent resident, and so on). And, the employee must sign the document under penalty of perjury. You must make sure that the employee completes this portion of the form no later than the end of the first day of work.
Next, the employee must provide documents as proof of identity and work authorization. Certain types of documents are enough, by themselves, to prove both (for example, a United States passport). Otherwise, the employee must provide one document from a specified list providing identity (such as a state driver's license, a U.S. military card, or a Native American tribal document) and one document from a specified list providing work authorization (such as a Social Security card, birth certificate from within the United States or its possessions, or a resident citizen identification card).
You must examine these documents and then verify that you have done so, that the documents appear to be genuine, and that, to the best of your knowledge, the employee is authorized to work in the United States. You must sign the form under penalty of perjury and provide some basic identifying information, too.
Once you have completed Form I-9, you should keep it in a separate folder with the I-9 forms completed for other employees. You may complete and retain I-9 forms in paper form or electronically. You must keep the form for as long as the employee works at your company, and for one year after employment ends or three years after the employee was hired, whichever period is longer.
You don't have to file I-9 forms with the government. Instead, you must keep them on hand and make them available for inspection by federal agencies, upon request.