Use the current agreed facts and assess material changes before relying on the filing or travel plan. A signature on an obsolete description does not authorize revised work.
Keep the change traceable
Retain the previous offer, the revised terms and the date the change was confirmed. Ask the actual employer to resolve differences in duties, entity or duration. An urgent start date should not cause the file to describe a role that is no longer offered.
The two long items usually sit outside the employer's control: a provincial regulator or registrar issuing a letter of standing, and a credential evaluation for a degree earned outside Canada or the United States. A professional order may take weeks to issue a confirmation of standing, a university transcript request has its own queue, and a U.S. employer's legal department may revise the letter several times. A Canadian citizen can apply at a port of entry on the day of travel, but redrafting the offer, obtaining transcripts and restructuring a contractor arrangement into employment are what consume the calendar. Renewal is also the step most often started last, once the offer, the credentials and the travel dates are already settled, and that ordering is exactly what turns a routine errand into an emergency.