Retain the executed escrow agreement, subscription agreement, wire instructions with the independent verification note, the outgoing transfer confirmation from your own bank, and the escrow agent's written acknowledgement of receipt. Add the statement showing the balance leaving your account and, later, evidence that funds were released into the enterprise.
Capture the receipt side too
Investors often keep proof that money left but not proof it arrived, and the path of funds needs both ends. Request written acknowledgement from the escrow agent on the day of transfer while the matter is active. If the transfer moves through correspondent banks or a currency conversion, keep the intermediate advices as well.
Store everything in one dated folder so the sequence can be reconstructed without relying on memory. Keep both ends of every transfer and the middle where one exists. The outgoing confirmation from the investor's own bank, the escrow agent's written acknowledgement of receipt dated the same day, and any correspondent bank advices together show the path the money took.
Add the statement showing the balance leaving the account, and later the evidence that funds were released into the enterprise. Store the set in one dated folder with a plain index, because the sequence has to be reconstructable years afterwards without relying on memory. Separately, retain the records showing where the money came from originally, since custody documents answer a different question from the source-of-funds requirement and neither substitutes for the other.