That it is a real operating business capable of employing the person: a qualifying relationship with the entity abroad, ongoing international business, secured premises suited to the work, funding, and supervision. New operations face requirements that established ones do not, and those differ by category, so counsel should confirm which apply.
Prove capacity with ordinary business records
Leases, incorporation and ownership documents, banking arrangements, insurance, supplier or customer agreements, and payroll set-up describe an operation better than forecasts. Photographs of an empty suite prove little. Where the operation shares space with a related entity or a service provider, say so and describe the arrangement, since an unexplained address that resolves to someone else's office invites questions the file should have answered.
Underneath the operating facts sits the transferee's own condition, and it is independent of how ready the office is. The applicant must have been employed continuously for one year within the three years preceding the transfer by a qualifying entity abroad, in a capacity that was managerial, executive, or involved specialized knowledge. A first review generally starts there, because an operation that is fully ready cannot rescue an applicant whose qualifying year falls two months short.
Reconstruct that year from payroll records, dated contracts of employment and, where the applicant has moved between related entities, the documents that establish the relationship between them.