The full history of the business sold, its financial statements and tax filings, the share ownership record, the purchase agreement with its price allocation, closing statements, and bank records tracing each dollar from the purchaser through her accounts into the investment. Any borrowing needs its own loan and security documents.
Build the chain forward from origin, not backward from the balance
Files are usually assembled by starting with a current bank balance and explaining it. Adjudicators read in the opposite direction, and so should the file. Solange should begin with how the Stratford business came to be hers, then how it earned, then how it was valued and sold, then how each tranche of proceeds moved.
That means incorporation records and the share ledger, several years of statements and returns, the sale agreement including any earn-out and holdback terms, the closing statement, and bank records for each account the proceeds touched, including any account outside Canada. Currency conversions and transfers between institutions each need a document. Where personal savings or an inheritance supplement the proceeds, those have their own chains and cannot be waved through as commingled.
Translation is required for anything not in English, and a chain with one unexplained transfer is generally treated as a chain with a hole in it.