Keep the relevant acquisition and account history, trade confirmations, settlement records and transfers, together with the lawful-source evidence required for the original funds. The exact period and documents depend on the actual case and current requirements. The last sale confirmation alone may leave the earlier source unexplained.
Distinguish market movement from money transferred
Record holdings sold, actual proceeds, charges and any currency conversion. Explain material transfers between accounts and who owned the assets. Obtain required historical tax and other records rather than assuming a universal short lookback.
If records are unavailable, ask counsel about appropriate authentic evidence; do not reconstruct a more favorable sale price than the transaction actually produced. Keep the records in the order the money moved, with the date of each step visible: acquisition, holding period, sale, settlement, transfer, receipt. A chronology assembled that way answers most questions before they are asked, whereas a folder sorted by account leaves the reviewer to build the sequence.
Where a document covers a period rather than an event, note both its start and end dates, since gaps between statements are what prompt requests for more. Ask the financial institution early how far back it will produce records and in what form, because an archive request can take considerably longer than a current statement and cannot be compressed once a filing date is set.