A Canadian citizen can apply at a port of entry as soon as the employer letter and credentials are ready, and start on admission. Filing Form I-129 in advance adds USCIS processing time but provides an approval before travel.
The letter sets the pace, not the mine's schedule
Hypothetical example: The U.S. operator may want Priya on site before the next planning cycle, but the timeline is governed by the document set. The employer letter usually takes the longest because HR must describe the duties correctly, and a poorly worded first draft often has to be rewritten. Transcripts ordered from a university can take weeks. Once the packet is complete, a Canadian citizen may present it at a port of entry or preclearance location and, if admitted, begin work that day for up to three years. If the employer instead files Form I-129, expect the USCIS processing time shown for that form and consider premium processing if the start date matters. Priya should not give notice at the Logan Lake contractor until admission or approval is in hand, because a refusal at the port leaves her with neither job.
Hypothetical example: A Canadian pharmacist is asked to begin after a hospital pharmacy opens a new wing. The decision sequence is credential availability, a duty letter that matches the professional role, and any separate state practice requirement. A licence application that remains pending may not prevent an immigration review, but it can prevent the promised work from starting lawfully. The employer should align the reporting date with both processes instead of treating admission as the only deadline.