Build a dated record that explains the work actually performed and supports the claimed duration.
Make the experience understandable
Employer records should identify periods, responsibilities and relevant systems work rather than only praise the applicant. Reconcile overlapping employment periods and unexplained dates. Experience evidence supplements the qualifying diploma or certificate; it does not remove that route’s educational requirements or the rest of the TN assessment.
A single description covering both phases, showing they are one professional assignment: the field program and its purpose, the interpretation and modelling that follow, the reports produced, the expected duration, and who within the employer directs and receives the work. A letter on company letterhead identifying the United States employer, naming the listed profession, describing the duties in that profession's terms, and stating the temporary duration, the salary and the work location. An offer letter states what the employer intends; a statement of work, purchase order or client services agreement states what was actually bought, and where those two describe different activities the second usually carries more weight because a third party signed it. Once the letter is right, the supporting documents simply corroborate it: proof of Canadian citizenship, the degree with a transcript, the provincial licence in good standing, and evidence of any experience the profession's rule requires.