Bank confirmations of irrevocable transfers, escrow released on an unconditional closing, non-refundable deposits, executed leases, paid equipment invoices and signed supply contracts. A deposit the buyer can recover by walking away evidences an intention rather than an investment.
Follow the money out of your control
Build the trail as a sequence of dated events rather than a folder of statements. Money leaves an identified account on a date, arrives somewhere on a date, and becomes irrecoverable on a date because of a specific contractual term. Each of those steps should have a document, and the terms that make the commitment irrevocable should be highlighted rather than left for a reader to locate in a schedule. Where funds sit in escrow, the escrow instructions themselves become important: conditions that permit return to the buyer keep the money out of the analysis, and everyone involved should understand that before the closing structure is fixed.
Hypothetical example: a buyer from Roxton Pond negotiates the purchase of a trim and stair-parts plant in the United States, and the agreement provides a substantial deposit that is fully refundable until a due-diligence period ends. Until that period expires, the deposit is not at risk. The workable answer is usually to sequence the application after the contingency lapses, or to restructure part of the payment as a non-refundable commitment the parties are genuinely content to make. What does not work is describing a refundable payment as an investment and hoping the escrow instructions go unread.