Before the employee begins the changed work. The employer should assess whether the new location affects duties, client control, the specialised-service arrangement or other facts supporting the existing case.
Use the itinerary as a checkpoint
Provide the new statement of work and reporting details early enough to identify any necessary immigration action. A travel booking or internal scheduling approval is not immigration clearance. Keep the employee and family informed of resulting timing changes, and distinguish review time from adjudication or admission steps rather than promising that every site can be added immediately.
Put one named person in the approval path for new sites. Sales teams commit to dates, schedulers assign engineers, and neither is asked whether the assignment still matches the petition. A single checkpoint, with authority to hold a deployment, is what converts a policy into a practice.
Hypothetical example: a customer asks for an unplanned week at a fourth distribution centre operated by a different logistics contractor. The question is not whether the engineer is available; it is whether the arrangement at that site still matches what was described. Give the checkpoint owner the questions to ask: who owns the site, who supervises there, and whether the phase is materially different.
Distinguish your own review time from any government step that follows it.