Do not assume a private effective date establishes immigration permission. Review the change and the applicable process before undertaking work that may exceed the existing authorization.
Align the employment change with the real permission
Locate the current admission or approval terms and the genuine revised duties. An employer’s internal personnel system cannot amend immigration status. Assess the next step using the actual facts rather than a payroll deadline.
A Canadian citizen may request TN admission from an officer at a land port or airport preclearance location with proof of citizenship, the prearranged professional employment, and the required credential. If the engagement is expected to continue past it, start gathering the employer's updated letter and any refreshed evidence weeks ahead, since collecting documents from a different country on short notice is what most often causes a gap. In parallel, the offer letter usually needs revision: human-resources departments write to internal templates, and the first draft rarely uses the language the listed profession requires. Employment letters from former employers, certified credentials and a properly drafted offer letter are the slow parts, and an advance petition adds processing time that varies.