Monthly statements for every account in the funding path, a general ledger with separate shareholder-contribution and shareholder-loan accounts, deposit detail identifying each credit, wire confirmations, and personal records showing where the money originated. Sales records such as invoices and merchant settlement reports should tie to revenue deposits, not to contributions.
Make each deposit explainable in one line
For every credit in the operating account, record the date, amount, payer and character: capital contribution, shareholder loan, customer payment, refund or internal transfer. Transfers between the investor's own accounts are movements of the same money, and counting them twice overstates the capital. Where support is thin, corrective entries with backup can be prepared; gaps can usually be supplemented before filing.
Scope the work first: how many months of statements, how many accounts, whether prior filings must be amended, and who writes the source-and-path narrative. Reconcile the difference using the actual transaction records and supplier explanation. Use a ledger that ties each bank statement, transfer, invoice, contract, and receipt to one business purpose. Create a money trail that begins before the transfer and ends with a specific business expense, then pair it with documents showing who will direct operations.
The practical decision is whether your spouse signs, whether a larger deposit or a letter of credit substitutes, and whether liability ends when the term ends.