Under current federal immigration laws, U.S. companies can only employ people who may legally work in the United States — be they U.S. citizens or foreign citizens who have the necessary work authorization. Since 1986, employers have been required to collect and maintain documentation for every employee they hire, verifying their legal status to work. This is done by the ubiquitous Form I-9.

E-Verify, which was created in 1997 initially as a pilot program, is an enhancement to prevent undocumented people from gaining employment. E-Verify is an Internet-based system that allows businesses to go online and quickly check a potential employee’s eligibility to work in the United States. E-Verify was created in part as a countermeasure to immigrants’ use of fraudulent documents necessary to support the declaration contained in Form I-9. E-Verify is fast and free, but the real question for employers is “Do I have to use it?”

For the most part, the answer is no. E-Verify is primarily a voluntary program. However, a number of companies may be required to use E-Verify. For example, some federal contractors are required to use E-Verify. This is not a function of law but of contract. In other words, the contract that the company enters with the government or the governmental agency may have a Federal Acquisition Regulation clause that specifically requires the contractor to enroll in and use E-Verify for the life of the contract.

In addition, a number of states have laws that require employers in those states to use E-Verify in some circumstances. Florida is not one of those states, but the neighboring states of Alabama and Georgia have such laws, along with at least six other states.

On June 27, the U.S. Senate passed a comprehensive bill designed to completely overhaul this country’s immigration laws. Under the Senate bill, E-Verify will be expanded and made mandatory for all employers over a period of five years. The bill requires identity verification through the use of enhanced fraud-proof documents, such as tamper- and identity-theft resistant Social Security cards and the use of a tool to allow employers to verify an individual’s identity through photos. If the Senate bill were to become law, it would take precedence over state and local laws on the hiring of foreign nationals, eliminating the current hodgepodge of state regulation.

Under the Senate bill, employers with more than 5,000 employees would have to use E-Verify no later than two years after publication of the regulations. Employers with more than 500 employees would have to use it within three years with an exception for agricultural employers, who would be given four years. All remaining employers subject to mandatory E-Verify would have to use the system within four years with an exception for Indian tribal government employers, who are given five years, as well as for employment that is “casual, sporadic, irregular or intermittent.”

Passage of the Senate bill came after a unique coalition, including both organized labor and pro-employer groups that came together on critical issues affecting employment opportunities in the U.S. The Senate bill now goes to much more conservative House. Speaker John Boehner has said the House will not take up the Senate bill but rather begin with its own bill.

As a result, it is uncertain what will happen to the Senate’s mandate of phased-in E-Verify. Even more uncertain is whether any immigration reform will pass the House in a version that is acceptable to both the Senate and president. Without comprehensive immigration reform, employers — especially those operating in multiple states — will be left with a patchwork of varying obligations when it comes to use of E-Verify. In fact, the failure of Congress to pass comprehensive immigration reform could lead to additional state laws on E-Verify. Employers need to review their existing obligations and stay tuned to see what develops.