It proves a transaction, not necessarily how the parent acquired the money or whether all relevant conditions are satisfied.
Connect the transfer to its lawful origin
Identify the source event and records available from the donor or lender, then trace the actual path to the investment. Keep currencies, deductions and dates accurate. Do not turn a missing historic statement into an invented balance or assume that a family relationship makes earlier source evidence unnecessary. Assess any evidentiary gap through the actual case process.
Documents covering the whole history of the value, not just its final form: corporate ownership records, auction and property sale documents, loan discharges, tax filings across the years, and an unbroken bank trail into the enterprise. Expect to provide financial statements covering the period in which the funds accumulated, corporate tax filings, the resolution authorizing any dividend or distribution, and banking records showing the movement. The professional work behind a source-of-funds file is substantial: an accountant reconstructing several years of company distributions, a lawyer assembling and presenting the chain, valuations for the property securing the loan, and certified translations where needed.