Different I-797 forms are issued. For example, an I-797C (Receipt Notice) is issued to confirm receipt of an application. If any questions arise about an application that is currently being reviewed by the U.S. immigration authorities, then the applicant will receive an I-797E (Request for Further Evidence).
Certain U.S. visa applications can only be submitted by the prospective employer, e.g., the U.S. company or agent of the applicant in the United States (petitioner) on behalf of each employee (beneficiary).
Should the employer apply for an L-1 visa on behalf of the employee, the prospective employer in the United States must make a petition to the competent service center of the Immigration and Naturalization Service (USCIS). This petition includes not only the application forms, but also extensive documentation about the U.S. company or group of companies, the position that the employee is filling in the United States, and the current activities of the foreign employee and his qualifications.
After reviewing the petition and application forms, the USCIS shall inform the U.S. employer in the next step in writing about whether the petition has been approved or rejected. This information is communicated by issuing an I-797 notice. If the petition is approved, the U.S. company will receive a so-called I-797 Approval Notice via the regular mail. The foreign employee will need this document to continue the U.S. visa application process during consular procedures.
The I-797 notice always contains information about the petitioner, beneficiary, the requested category, as well as a transaction number under which the application is being processed. The approval notice in particular will disclose the period of validity (i.e., the authorization period) of the work permit, for example.