Collect the relative's statements covering each disputed payment, the invoices and receipts they settled, a written declaration of the arrangement, evidence of the relative's own lawful source, and the investor's records showing reimbursement or the funds' origin. Add corporate books recording capital contributions so the enterprise's accounts agree with the bank trail.
Redact carefully, explain fully
A relative may not want every unrelated transaction read. Provide complete statements for the periods that matter and discuss with counsel what may reasonably be limited, since removing pages can look like a gap. Where a record no longer exists, request a bank certification and say plainly what was lost and why. Files are commonly supplemented after a first review; plan for a second collection round rather than treating the first as final.
From the partner: several years of financial statements and business tax returns, current payroll showing employees, the main service contracts, state licences for the trade, the premises lease, vehicle and equipment lists, and the existing formation and ownership documents. Signed purchase documents, lease terms, payroll assumptions and opening invoices establish the denominator; bank confirmations and irrevocable payment obligations show what is exposed to loss.
Have the new company pay business expenses from its own account, with invoices addressed to it, so the ledger reads cleanly later.