The primary risk in this scenario is the inaccurate manual transcription of totals from a source document (spreadsheet) to a target system (job-costing system). Reconciliation is a detective control that directly addresses this risk by comparing the totals from the source with the totals entered into the system. This control provides the highest level of assurance that the overall data transfer was accurate and complete. While other controls are useful, reconciliation is the most effective method for verifying that the final, aggregated figures in the system match the source.

B. Validity checks only ensure the correct data type is entered (e.g., numeric vs. character) but do not verify the accuracy of the number itself.
C. Reasonableness checks only confirm that an entered value falls within a plausible range, not that it precisely matches the source document.
D. Displaying entered data for visual verification is a weak control because it relies on the data entry person to notice their own error.

1. ISACA. (2019). CISA Review Manual

27th Edition. Schaumburg

IL: ISACA. In Domain 3: Information Systems Acquisition

Development

and Implementation

the section on Application Controls describes reconciliation as a key control to "ensure that data is complete and accurate throughout its processing." It specifically contrasts this with input controls like validity and reasonableness checks

which are preventive but do not guarantee accuracy against a source document.

2. Weber

R. (2012). Information Systems Control and Audit. Pearson. Chapter 12

"Auditing Computer Applications I

" explains that while input validation controls (like validity and reasonableness checks) are important preventive measures

detective controls such as reconciliations are essential for ensuring the accuracy and completeness of data that has been processed. Comparing source data totals to processed totals is presented as a fundamental reconciliation technique.

3. Singleton

T. (2013). IT Auditing and Application Controls for Small and Mid-Sized Enterprises. ISACA Journal

Volume 5. This article emphasizes that for manual data entry processes

reconciliations are a critical compensating control to detect errors that preventive input controls may miss

thereby ensuring data integrity between different stages of processing.