Read the official page and FAQ for the current list first. Expect identity documents, civil records, evidence of the lawful source of the gift funds and whatever the official form requires for vetting, plus documents for the underlying employment-based process.
The official list, then the standard immigrant file
Hypothetical example: the couple begins by requesting a bank letter confirming they can afford the gift. That may be useful, but the official framework describes vetting, so the file should resemble any immigrant application: current passports, birth and marriage certificates, the physician's retirement and income records showing the lawful source of the funds, and whatever the official form or FAQ requests. Because permanent residence is obtained through an employment-based category, additional documents may be required at the petition and visa stages.
Save a dated copy of the official instructions in force when the application is made and check any adviser's list against it. Certified English translations are required for any French record. If a document cannot be obtained, note the reason and ask the official process what alternative evidence it accepts rather than substituting an informal statement.
A document review should preserve dated official instructions, identity records, proof of the applicant's funds, payment confirmations, and civil documents for any family member seeking a related benefit. It should distinguish a government notice from an adviser summary. Hypothetical example: a conservator of historic organs keeps a screenshot of a news article but no copy of the official guidance.
The reviewer downloads and dates the official material, notes the version consulted, and files the payment and identity documents separately. That record makes later changes easier to identify and reduces reliance on informal descriptions.