At closing, not at the next renewal. The qualifying relationship must exist throughout the period of stay, so a gap between a transaction and its assessment is a gap in which the facts and the approval have diverged. Reviewing at closing also gives time to file an amendment before anything else changes.
Close the transaction and review the same week
Corporate transactions have their own timetable and immigration is rarely on it. Add one item to the closing checklist: identify every employee whose status depends on the corporate structure, and have counsel confirm whether the transaction preserves, alters or ends the qualifying relationship. Promotions should likewise be reviewed before they take effect because a change in L capacity can require an amended petition.
A relocation should be assessed case by case; a worksite change alone does not automatically require an L-1 amendment if the employer, duties and eligibility facts remain the same. Finally, keep the seven-year L-1A maximum in view, since no reorganization restarts it.