Identify the actual immigration permission and any separate practice requirements before relying on the work. A proposed qualification basis is not itself authorization.
Check both prerequisites
Do not treat one process as automatically completing the other.
Set dates for receiving the employer letter, credential review, licence confirmation, family document checks, and the intended immigration procedure. Start with whatever takes longest: a credential evaluation if any degree is foreign, then the employer letter revision, then transcripts, then the passport check. Build backwards from the proposed first workday and allow time to correct a letter, obtain an original credential, or resolve a name difference. Ask the employer when the revised duties begin, identify what must be resolved beforehand and keep the start flexible until the relevant assessment is complete.
A Canadian citizen may request TN admission at an eligible port of entry or preclearance location, or a prospective employer may file Form I-129, but neither option converts incomplete licensing or certification into permission to practise. Where the employer needs cover in the interim, that is a staffing question to be solved separately rather than a reason to compress the immigration one, and saying so early usually produces a better conversation than discovering it after a second attempt.