Correct Option: D. Sales invoice and debit note Explanation of the Correct Answer Source Documents Defined: Source documents are the original records that contain the details of a transaction. They serve as the foundation for recording financial transactions in the accounting system. These documents provide evidence that a transaction occurred and include essential information such as the date, amount, parties involved, and nature of the transaction. Why Option D is Correct: 1. Sales Invoice: - A sales invoice is a document issued by a seller to a buyer. It details the products or services provided, the amount due, and the payment terms. This document is crucial because it serves as proof of the sale and is used to record revenue in the accounting books.

1. Debit Note:
2. A debit note is a document sent by a buyer to a seller, indicating a return of goods or a request for a reduction in the amount owed. It serves as a source document because it provides evidence of a transaction that affects the accounts, such as a return of inventory or an adjustment to a previous sale.

Both the sales invoice and the debit note are primary documents that initiate the recording process in accounting, making them valid source documents. Why the Other Options are Incorrect or Weaker Option A: Journal and Ledgers - Explanation: - Journals and ledgers are not source documents; rather, they are part of the accounting system used to record and summarize transactions. - A journal is where transactions are first recorded (journal entries), and a ledger is where these entries are categorized and summarized by account. They rely on source documents for their information but do not serve as evidence of transactions themselves. Option B: Sales Invoice and Cash Book - Explanation: - While the sales invoice is indeed a source document, the cash book is not. - A cash book is a record of cash transactions (both receipts and payments) and is used for tracking cash flow. It is a secondary record that summarizes transactions but does not serve as the original evidence of a transaction. Option C: Cash Book and Debit Note - Explanation: - Similar to Option B, the debit note is a source document, but the cash book is not. - The cash book, as mentioned earlier, is a record of cash transactions and does not provide the original evidence of a transaction. It is derived from source documents but does not qualify as one itself. Summary of Key Points

• Source Documents: Original records that provide evidence of transactions (e.g., sales invoices, debit notes).
• Sales Invoice: Proof of sale, detailing products/services and payment terms.
• Debit Note: Document indicating returns or adjustments, serving as evidence for accounting entries.
• Not Source Documents: Journals, ledgers, and cash books are secondary records that summarize transactions but do not serve as original evidence.

This thorough understanding of source documents is crucial for accurate financial accounting and ensures that all transactions are properly recorded and verifiable.