1. The Audit Trail and Evidence
 
An accountant cannot record a transaction based on memory or verbal agreements. Every entry in the accounting system must be backed by verifiable, objective evidence known as a source document. These documents establish the audit trail, allowing internal and external auditors to trace financial statements back to the original business event.
 
2. Detailed Breakdown of Source Documents
Sales and Purchase Transactions
  • Invoices: Sent by a seller to a buyer when goods or services are provided on credit. It details the quantity, price, terms of payment, and total tax. For the seller, it is a Sales Invoice; for the buyer, it is a Purchase Invoice.
  • Credit Notes: Issued by a seller to reduce the amount a customer owes. This happens when goods are returned due to damage, or if the customer was overcharged.
  • Debit Notes: Issued by a buyer to a seller to formally request a credit note, or issued by a seller to correct an undercharge.
Cash and Liquidity Transactions
  • Receipts: Acknowledgments issued immediately when cash or electronic payment is received.
  • Bank Statements: Monthly summaries generated by the financial institution that verify all cash movements into and out of the company’s bank account.
  • Petty Cash Vouchers: Small, internal forms used to track and authorize minor cash expenses (e.g., office supplies or taxi fares).
Internal Adjustments
  • Journal Vouchers (JV): Documents used to authorize and record non-cash or internal adjustments, such as depreciation or correcting errors.