The current organisational chart, delegation-of-authority schedules, board or shareholder resolutions recording appointments, the transition plan with dates, and the successor's employment records abroad. Add the post-handover ownership documents. Records the business created at the time carry more weight than summaries written afterwards.
Use documents the business made for itself
Signing authority schedules, budget approval limits and minutes recording an appointment describe real authority in a way narrative cannot. Collect them as they exist, including versions from before the handover, so the change itself is visible. Where the transition is still being negotiated, note what is settled and what is not.
Ask counsel which gaps genuinely matter before commissioning new documents to fill every one of them. Collect the pre-handover versions alongside the current ones, since the comparison is what demonstrates that authority actually moved rather than being described as having moved. A signing authority schedule showing the predecessor's limits, and a later one showing the successor's, makes the point in two documents.
Where a transition is still being negotiated, record what is settled and what is not rather than presenting the intended end state as though it were in place. Ask counsel which gaps genuinely matter before commissioning new documents to fill all of them, because in a handover almost everything can be documented and very little of it is decisive.