Confirming that a figure computed one way equals the same figure computed another way, most often that a sales roll-up equals the number finance reports for the same period and definition.
Zero variance, for the same period and the same definition. Where definitions differ, for example gross bookings against net revenue, the difference is a named adjustment line, not an unexplained gap.
Values are numeric. Every level is filled. The hierarchy is a tree. No duplicate rows. Level totals agree with the grand total. Run in that order, each failure leaves a fingerprint at a specific level.
It means every exception is visible: "3 rows with no region, £4,300, listed below". The number is trusted because the exceptions are named, not because there were none.
The same figure is computed two ways, most often a sales report total and the finance ledger for the same period, and every difference is listed as a named reconciling item.
Sales report $4.20 million, ledger $4.23 million. Difference $0.03 million: intercompany sales of $0.05 million excluded from the report, less $0.02 million of credits dated after the export.
Differences explained as timing, with no list. The gap grows each month until nobody trusts either number.