The complete chain: how the business was built and owned, the sale agreement, the proceeds received, the taxes paid, and every transfer from that point to the investment.
Every step in the path needs a document
Hypothetical example: Source-of-funds review looks at both where the money came from and how it travelled. For a share sale that means incorporation and shareholding records showing the family's interest, the purchase and sale agreement, closing statements, the bank record of proceeds arriving, and the tax filings reporting the gain. If proceeds were held in a holding company, invested, or divided among family members before reaching the investor, each of those movements needs its own explanation and record. Gifts and loans within a family are permissible but require their own documentation of the giver's lawful source. The failure that causes most delay is a period where money sits in an account with no evidence of what it was or where it came from.
Prepare a dated source-and-path ledger that links the original asset, each sale or loan followed by each movement into the project. Hypothetical example: A commercial-bakery owner uses business-sale proceeds accumulated through several shareholder distributions. Sale agreements, corporate records, tax documents plus bank records must explain each link. A statement that the money was earned honestly does not replace the records that show how it moved.
Retain records in chronological order and explain any unusual transfer before filing. This is easier than reconstructing a complicated transaction years later.