In a reconciliation runbook, what defines the rules for matching data from different sources?

• A. Data Sources
• B. Mapping Rules
• C. Thresholds
• D. Alerting

Answer: (B)

Mapping rules define how fields from different systems are aligned and compared during reconciliation. They specify which data elements to compare, how values should be transformed and normalized (such as trimming whitespace, standardizing date formats, or case adjustments), and the logic that determines a match (exact equality, tolerances for numeric differences, or even fuzzy matching). This is why mapping rules are the best answer—they encode the concrete instructions for relating and evaluating data across sources so the reconciliation can consistently determine matches. Data sources provide the actual data, thresholds may influence whether a result is accepted or flagged, and alerting handles notifications; none of these by themselves define how the matching is performed across sources.