Final answer:
The CPA can trace transactions from the billing register to the accounts receivable ledger to determine if all customers are being billed accurately.
Step-by-step explanation:
The CPA auditing an electric utility can determine whether all customers are being billed by tracing the transactions from the billing (sales) register to the accounts receivable ledger. This direction of test helps ensure that all sales transactions are accurately recorded in the accounts receivable ledger, which represents the amount owed by customers.
By comparing the entries in the billing register to the corresponding entries in the accounts receivable ledger, the CPA can verify if all customer bills have been properly recorded. If any discrepancies or missing entries are found, further investigation can be done to identify the cause and rectify any errors or omissions.
For example, if the billing register shows that a customer was billed for a certain amount but that entry is not found in the accounts receivable ledger, it may indicate a failure to properly record the transaction and bill the customer. This could result in lost revenue or inaccurate financial statements.