The source document is the original record of a transaction. During an audit, source documents are used as evidence that a particular business transaction occurred. Examples of source documents include:

• Cash receipts
• Credit card receipts
• Cash register tapes
• Cancelled checks
• Customer invoices
• Supplier invoices
• Purchase orders
• Time cards
• Deposit slips
• Notes for loans
• Payment stubs for interest

At a minimum, each source document should include the date, the amount, and a description of the transaction. When practical, beyond these minimum requirements source documents should contain the name and address of the other party of the transaction.

When a source document does not exist, for example, when a cash receipt is not provided by a vendor or is misplaced, a document should be generated as soon as possible after the transaction, using other documents such as bank statements to support the information on the generated source document.

Once a transaction has been journalised, the source document should be filed and made retrievable so that transactions can be verified should the need arise at a later date.