Recording sole-proprietor income and proving it without an invoice

A sole proprietor does not separate "business money" from personal money — what matters is recording all income and expenses regardless of which account or wallet they sit in (Wise, PayPal, a bank, or cash). Income is considered received, and must be declared, at the moment the client actually pays, not when funds are later withdrawn from an intermediary service. Cash taken from the business account for personal use is recorded either as 事業主貸 ("drew business funds for personal expenses") or as a transfer (振替) between accounts. If a payer does not issue invoices — for example, a platform like Outlier AI — any document showing the amount and basis of the payment is enough to prove income in case of an audit, such as a screenshot of the platform's payout dashboard.