Which assertion is verified by tracing transactions from source documents to journal entries?

Tracing transactions from source documents to journal entries primarily validates the completeness assertion. The completeness assertion ensures that all transactions that should be recorded in the financial statements are actually recorded. By tracing from the source documents—like invoices or receipts—back to the journal entries, the auditor verifies that each relevant document has been accounted for and has resulted in an appropriate entry. This process is critical for identifying any transactions that might have been omitted from the accounting records.

In contrast, the existence assertion focuses on ensuring that recorded transactions actually occurred and are valid. The valuation assertion pertains to the accuracy of amounts recorded in the financial statements, ensuring that assets and liabilities are recorded at appropriate amounts. Lastly, the rights and obligations assertion deals with confirming that the entity has rights to its assets and obligations for its liabilities. Each of these assertions has a specific investigative approach, making the tracing process particularly relevant to the completeness assertion.