The full chain from origin to investment: the shareholders agreement, the redemption resolution and valuation, the promissory note, records of each payment received, tax returns and assessments, and bank statements tracing the money into the investment. A matrimonial settlement contributing funds must be documented on the same standard.
Every dollar has to have a history
The lawful source and path requirement is documentary rather than argumentative, and it is usually the longest part of the file. Start at the origin. For a share redemption, that means the agreement that created the shares, the agreement that governs their redemption, the corporate resolution, the valuation that set the price, and the note itself.
Then follow the money: each payment, the account it entered, and the tax reporting of it. Personal and corporate tax filings for the relevant years support the picture. Where funds come from a second source, that source needs the same treatment, so a matrimonial property settlement is evidenced by the separation agreement or court order and by the transfer records, not by an explanation.
Gifts and loans from family members are the usual weak point in these files, because they are described rather than proved. If a source cannot be documented, it is better to leave it out and invest less than to include it and have the whole file questioned.