Treat the date as a planning target while the underlying eligibility, evidence, and chosen process are still being reviewed. TN preparation and the actual government decision are separate steps, and an expected date is not itself authorization to begin work.
Identify the next fact that still needs confirming
Ask what remains to be confirmed before the support letter can be finalized, and who controls that information. Check current port-of-entry or petition procedures before booking non-refundable travel. If the employer, duties, or assignment changes, ask for a reassessment rather than assuming the original review still applies, and consider the applicant's broader immigration history and intent independently of the offer's urgency.
A Canadian outside the country may request TN admission through border inspection or preclearance, or the employer may submit an I-129 petition to USCIS when that route fits the facts. A revised duty description waits on an employer's internal approvals; a registration confirmation waits on a regulator's queue; and where a petition route is used, processing waits on nobody in the room. An evaluation provider, a licensing board, a foreign university asked to verify a transcript, a professional body confirming standing — each has its own queue and none of them will treat this as urgent.