Which of the following is not a source document?

A source document is the original piece of paper or electronic record that provides evidence that a transaction has taken place and supplies the details (date, amount, parties involved) needed to make an entry in the books of account. Examples used in bookkeeping include invoices, credit notes, debit notes, receipts, cheques, and petty cash vouchers.

An invoice is issued when goods or services are sold on credit and shows what is owed. A credit note is issued to reduce an amount owed, typically when goods are returned by a customer. A debit note is issued to increase an amount owed or to request that a supplier's invoice be corrected. Each of these is created specifically to record and support a business transaction, so each qualifies as a source document.

A bank note, however, is simply a unit of currency, a piece of paper money used as a medium of exchange. It does not record the details of a transaction and is not raised to provide evidence for a bookkeeping entry, so it cannot be classified alongside invoices, credit notes, and debit notes as a source document.

Examination tip: when a question lists "source documents," check whether the item records transaction details (who, what, how much) or is simply a form of money; only the former qualifies.