Ask for the source and meaning of the inputs relevant to the case, with appropriate professional explanation.
Keep the model tied to evidence
Distinguish actual expenditure or activity from forecasts. Do not invent an input to reconcile inconsistent versions or treat a summary chart as the full methodology.
A simple running file — annual financial statements, quarterly project reports, payroll summaries, evidence of any capital movement — turns the eventual filing into a summary exercise. For a gift, produce a signed gift instrument, evidence of how the donor lawfully acquired the funds, and the transfer record; a gift letter without the donor's financial history leaves a gap in the lawful-source evidence. For a household whose funds come from professional salaries, a property sale and perhaps a family gift, that means tax filings across years, sale documents and closing statements, statements for every account involved, and independent documentation of any giver's or lender's own source. The usual mistake is documenting the final balance while leaving scheduled receipts or an intervening account unexplained; a summary affidavit cannot replace missing transaction evidence. Keep the personal source-of-funds file, meaning sale contracts, tax returns, loan documents, and transfer receipts, physically separate from company records, since the two answer entirely different questions.