Prepare the factual position description, remuneration and intended period, plus the identity and qualification records the applicant will rely on. Resolve any material difference between the offer, a client statement of work, and the proposed support letter before it is finalized.
Let each party verify its own facts
The applicant supplies credential and identity records, while the employer verifies the actual work arrangement, including any staffing or subcontracting structure. If a staffing agency and an end client describe different responsibilities, ask them to reconcile the discrepancy rather than choosing whichever version sounds more favourable. Preserve dated versions and identify which is current.
Build the package around proof of Canadian or Mexican citizenship, the credential demanded by the selected profession in Appendix 2 to Annex 16-A of USMCA, and evidence of prearranged professional activity. That assignment may serve an American company or remain under foreign employment, yet it cannot be self-employment. The core evidence is an employer letter or contract; it should identify duties, duration, remuneration, and the actual employing arrangement. Gather diplomas, licences, transcripts, and evaluations only as the profession’s rule makes them relevant. The frequent error is allowing a client agreement, offer, and support letter to describe materially different jobs.
Hypothetical example: an Ottawa analytical chemist employed by a Canadian laboratory is assigned to troubleshoot testing methods at an American manufacturer. Counsel would compare the Canadian employment record, assignment contract, host-site description, chemistry degree, passport, and proposed letter before anyone signs. Because a foreign employer can support prearranged activity, the documents should explain that real structure plainly instead of recasting the manufacturer as the employer. They must also avoid implying that the chemist will independently sell consulting services.