With the sale agreement and closing statement, the allocation between shares and assets, corporate financial statements and tax filings, the lawyer's trust records, personal tax returns and a continuous bank trail to the investment.
The value has to be explained, not just the transfer
Hypothetical example: the couple can show the sale proceeds arriving in their account and assume that settles it. Often it does not, because the question extends to how the business came to be worth that amount. Provide the corporation's financial statements and tax filings for a period of years, the personal tax returns showing income drawn, and the accountant's working papers on the valuation if one was prepared.
Then the transaction: the agreement, the closing statement, the allocation of the price, any vendor financing, the trust ledger and the disbursement. Then the path: every account the money touched, with statements and matching amounts, including any currency conversion. Prepare a short written narrative with document references so a reader can follow the chain without assembling it themselves.