Authorization to be employed in the U.S. in a non-immigrant visa status is quite limited. Most visas which authorize employment in the U.S. restrict it to a specific employer and a specific position. In order to employ the foreign national, an employer is required to file an application (called a petition) with the USCIS to request permission to employ the particular foreign worker. The foreign worker may not begin employment until the USCIS indicates approval of the employer's request. The foreign worker is only permitted to work for the petitioning employer and is generally prohibited from working for, or receiving compensation from, any other entity.