The employment agreement with the repayment clause, any board or officer authorisation to make the gift, the offer letter, and every email or note recording what was promised orally. Keep executed versions where signing is required, and preserve dated correspondence in its original form. Incomplete records can prompt a request for evidence or contribute to a refusal, so gather them while people are willing.
Preserving what was said, not only what was signed
Public and oral statements by a sponsor can be legally relevant, so keep them: write a dated note after each conversation and confirm the substance by email. If a notice or an internal document contradicts what you were told, do not repeat either version as settled fact — investigate the conflict and ask your representative which record governs. Government notices themselves can contain errors, and a discrepancy is worth raising rather than absorbing.
Keep the official notice and the private service agreement distinguishable. Once a visa is available you attend an interview, complete the required medical examination with an authorised physician, and submit whatever additional documents the consular officer requests. Build a notice-response matrix showing each request, its deadline, the exact evidence available and any point that needs explanation. Following successful vetting, officials request a US$1 million gift for the United States.