Provide proposed or effective changes promptly, with the actual dates and records, so implications can be assessed before travel or reliance on the revised arrangement.
Coordinate before documents and facts diverge
Identify the current employer, duties and relevant company relationship. Do not wait until an unexplained mismatch appears during travel or employment verification to determine what the change actually means. The reporting trigger should be the proposal, not the completion.
By the time payroll shows a new name the change is done, the effective date is fixed, and the options that existed while it was being planned have closed. Ask the employer to notify the immigration professional when a corporate change is contemplated and expected to affect the entity employing transferred staff, and give that instruction to whoever would know first, usually in a legal or corporate function rather than in the operating unit. Where notice arrives late, the question narrows and sharpens: what is the applicant doing right now, for which entity, and does anything need to stop while the position is assessed?
Answer that before turning to the documents. A file where paperwork is being corrected while work continues under an unexamined arrangement has the two tasks in the wrong order. Agree who makes that call, too, so the decision is not left to the person with the least information about what the change means.