Prepare the factual position description, pay, and intended period from the employer, plus the applicant's citizenship and qualification records. Resolve any difference between the offer and a separate support letter before relying on either.
Let each party document what it can actually confirm
The applicant supplies credential and identity evidence; the employer confirms the position and reporting relationship. If a staffing agency and an end client describe the assignment differently, ask them to reconcile the accounts before filing. Keep dated versions of every document and identify the current one; a well-written letter cannot substitute for an unconfirmed detail.
The transcript for the engineering degree, the provincial permit if relied upon, proof of citizenship, and a draft of the U.S. entity's letter to compare against the internal transfer memo. A degree conferred under one surname, a provincial registration under another and a passport under a third is not evidence of anything wrong, but it is evidence of nothing at all until the connecting document is in the folder. The complete TN package must still prove citizenship, a prearranged professional engagement, a listed USMCA occupation, and the category-specific qualification.