This page discusses the general requirements for a non-U.S. citizen to lawfully accept employment in the U.S., assuming that the individual does not already have some type of work authorization (e.g., greencard). It does not address family based avenues of immigration (for individuals who have family members in the U.S. willing to sponsor them for U.S. immigration benefits); nor does it discuss any special immigration programs which may be available to persons meeting special circumstances, such as: the green card lottery, asylum, special protected status sometimes offered to individuals from particular countries, experiencing turmoil; or individuals who were born in the U.S. but departed when they were infants, etc.
First, the general rule of U.S. law is that in order for any non-U.S. citizen to accept employment in the U.S., he or she must have some type of work authorization from the U.S. government. This "work authorization" takes several different forms. Sometimes it takes the form of a visa, in the sense that certain visas include "work authorization", within certain conditions, as incident to the particular status. Examples of this are the H-1B visa, and the L-1 . Similarly, the B-1 visa (for individuals on business trips) contains some very limited employment provisions for completing business work for a foreign employer.
On the other hand, sometimes "work authorization" is not automatically included with the particular visa, but can be petitioned for by showing that one meets certain qualifications. For example, the F-1 visa, for students, does not automatically include work authorization, but the F-1 visa does provide for certain types of work authorization to be requested, such as "practical training" work authorization.
In addition, apart from temporary visas, work authorization is also provided for any non-U.S. citizen who obtains "permanent residency" in the U.S. This is what is commonly referred to as the "green card" (based on their original color, although they are no longer green). There are a number of different avenues for obtaining permanent residency, as discussed on our permanent residency page; however, in general the process is much more lengthy than obtaining a temporary work visa.
There are basically two types of temporary work visas and avenues for obtaining permanent residency: the first involves being "sponsored" by a U.S. employer; and the second involves sponsoring oneself. The latter, sponsoring oneself, however, is generally only available to persons with extraordinary or exceptional abilities, as defined by U.S. immigration law (which has gotten ever more strict in its definition of these qualifications). Consequently, the vast majority of individuals obtaining work authorization in the U.S. each year do so by being sponsored by a employer, for a particular type of visa.
Furthermore, U.S. law favors persons who are highly skilled, such as professionals (e.g., engineers, physicians, teachers, etc.), or persons who are entering the country to fill positions for which no U.S. worker can be found. Similarly, there are certain visas (such as the E-2) which are available for investors of a substantial amount of capital into a U.S. enterprise, which they will actively direct.
Consequently, for most individuals seeking U.S. employment, the first order of business is determining whether one's occupation qualifies for a temporary work visa. If such a visa is available for one's occupation, then one must either obtain a employer willing to sponsor one for such a visa; or (e.g., in the case of a L-1 intracompany transferee) request that one's employer transfer one to the U.S.