Corporate registration documents, ownership or shareholding charts, and any agreement describing the intercompany relationship address the first element. For the employment history, contracts, payroll records, tax filings and dated organisational charts carry more weight than a résumé, because they show continuity and who the actual employer was.
Collect evidence the company already generates
Most of this material exists in finance and human resources systems and only needs to be located, dated and organised. Where records sit with a foreign affiliate, start the request early, since retrieval often depends on people with no involvement in the transfer. Translations may be needed for some documents; confirm which ones with counsel rather than translating an entire personnel file in advance.
Start the foreign affiliate's retrieval first, because it is the request most likely to sit unanswered. A payroll or human resources team abroad has no involvement in the transfer, may not know why the records are wanted, and will treat the request at the priority it appears to deserve. Explain the purpose, name a date, and ask a specific person rather than a function.
Where records predate a system migration, ask what the organisation retained and in what form, since a partial answer obtained early leaves room to fill the gap from tax filings or the employee's own copies.