1. I-797A-I-797A is issued by the USCIS to the applicant with an I-94 approving the extension of stay in the U.S. This typically means that the change of status(F1 to H1, L1 to H1) has been approved and the candidate can legally continue working in the United States. When an I-797A is received by the petitioner, this must be handed over to the applicant and the H1-B holder must preserve it for future purposes such as visa stamping, etc. 2. I-797B-An I-797B is issued either to an applicant who doesn’t reside in the United States and has been applying from his home country or also to a person residing in the United States. In the second circumstance, the USCIS approves the H-1B petition to the applicant residing in the U.S, but doesn’t approve the change of status. 3. I-797C- When a petition for H-1B has been approved, the petitioner also receives an I-797C form along with the I-797A for the applicant. The petitioner must preserve this document for future references and communications with the USCIS as well as any queries from the U.S. Consulate. I-797C form is also issued to the petitioners to respond on rejection of applications, communicate on payments, interviews, reopen cases and setting up appointments, etc.