Source documents of an accounting system:

Source documents are those documents that identify the particular transaction that is being recorded.  They act as an internal control procedure to ensure that only valid transactions are recorded into the accounting system and as an audit trail so that individual transactions can be traced if required.

Examples of source documents would be:

• Invoices: provided by suppliers
• Receipts: issued by the organisation when payments are made to it
• Cheques butts: records the payment of accounts
• Contracts
• Transaction notification statements: issued when accounts are paid on-line
• Expense authorisations: usually an internal document authorising the expenditure of petty cash etc