Final answer:
Placing the account number in the Post. Ref. column signifies that the transaction has been posted to the ledger, ensuring accuracy and creating a traceable link between the journal and ledger.
Step-by-step explanation:
The significance of placing the account number in the Post. Ref. column of the journal as the last step in the posting procedure lies in ensuring accuracy and providing a clear audit trail. By recording the account number, it indicates that the entry has been posted to the corresponding ledger account. This step helps prevent errors and provides a reference point that can be used for reviewing the journal and the ledger for accuracy. It is the link between the journal where transactions are initially recorded and the ledger where they are classified.
Additionally, this practice is crucial during an audit, as it allows auditors to trace each transaction through the accounting system with ease, ensuring that all financial data is accurate and properly recorded. It simplifies the process of locating both the origin of a transaction in the journal and its impact on the accounts in the ledger.