Annual financial statements for both entities, current share registers, the organisation chart updated as it changes, payroll for the receiving company, and the transferee's travel record. These are the documents an extension is built from, and they are far cheaper to keep than to reconstruct several years later.
Keep the record as it is generated
An extension is a fresh evidentiary exercise, and the material it needs is created continuously by an operating business. Financial statements for both companies establish that each is still doing business, which is a continuing requirement. Share registers establish that the relationship still exists in the form that was approved, and they change more often than people expect through estate planning, buy-sell arrangements and financing.
The organisation chart establishes that the role is still managerial, and it is the document most likely to be out of date, because staff join and leave without anyone updating it. Payroll for the receiving company supports both points. The travel record supports any later recapture claim and is worthless if compiled from memory.
A single annual review, scheduled like a financial year end, keeps all of it current and turns extension preparation into assembly rather than investigation. Hypothetical example: a water-treatment equipment company plans to move its regional director after acquiring a U.S. distributor.
The first review produces two evidence files: corporate records showing ownership and control, and personnel records proving her qualifying employment abroad. The purchase agreement, ownership register, tax filings, payroll, and organisation charts settle the company side; employment letters, pay records, and duty descriptions settle the individual side. The company should collect dated records before a reorganisation obscures the relationship.
A vague group chart or an executive title without evidence of actual authority leaves the core point unproved.