The answer to your question depends on your current immigration status in the United States. If you already have H-1B status and are in the United States to work for your H-1B employer, you can begin working for a new employer as soon as the new company files an H1-B transfer petition on your behalf. If you do not have H-1B status, you must wait until the U.S. Citizenship and Immigration Service (USCIS) approves your H-1B visa before you can legally start working.
Processing times will vary depending upon your service center. You may be forced to wait a few months for clearance. If your employer can show a compelling reason why you need to start working for them immediately, USCIS might approve the petition sooner. Employment cannot begin, however, until USCIS has issued the appropriate visa.
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