According to the CRISC Review Manual (Digital Version), the best way to mitigate the risk associated with data integrity loss in the new payroll system after data migration is to compare the processing output from both systems using the previous month’s data, as this ensures that thenew system produces the same results as the old system for the same input data. Comparing the processing output from both systems using the previous month’s data helps to:

Verify the accuracy and completeness of the data migration process and identify any errors or discrepancies in the data transfer

Validate the functionality and performance of the new system and confirm that it meets the business requirements and expectations

Evaluate the consistency and reliability of the data processing and reporting in the new system and detect any anomalies or deviations

Recommend and implement appropriate actions or measures to address any issues or findings in the data migration and the new system

Communicate and coordinate the data migration and the new system testing with the relevant stakeholders, such as the data owners, the users, and the senior management

References = CRISC Review Manual (Digital Version), Chapter 2: IT Risk Assessment, Section 2.4: IT Risk Scenarios, pp. 107-1081