US work visas requires the prospective employer to first file a petition with U.S. Citizenship and Immigration Services (USCIS). A job offer is required and the U.S. employer must file an Immigrant Petition for Alien Worker, Form I-140, on behalf of the applicant.Search all USCIS forms. File your form online for a more convenient and secure experience. As part of the interview I need to share a job offer letter. My employer wants to write it but needs to know what all should go inside the letter. In this blog article, we explain the purpose of an immigration recommendation letter and offer guidance on writing an effective one. You'll need also a Letter of employment for the time you were working for your employer, including NOC, Salary, duties, dates and worked hours. Following receipt of a tentative selection letter, you must complete preemployment requirements. This offer letter comprises the complete terms of the offer regarding your employment.