A parallel run is a controlled operational period in which the new system operates alongside the legacy system — both processing the same transactions, both producing outputs, and the outputs being reconciled against each other to confirm that the new system produces correct results before the legacy is decommissioned. It is the most rigorous form of go-live validation available: rather than testing in a test environment with test data, the parallel run validates the new system using live business data in the live production context. Any discrepancy between the legacy system’s output and the new system’s output requires investigation and resolution before the legacy system is switched off.
Why This Matters in GCC and Egyptian Enterprise Programmes
Parallel runs are particularly valuable for financial consolidation system replacements in GCC group structures, where the stakes of an incorrect consolidated balance sheet or income statement — in terms of board credibility, regulatory submission, and audit opinion — are very high. Running the first live consolidation on a new system, reconciling it against the last consolidation produced by the legacy system, and having the finance team confirm that the new system’s output represents an accurate picture of the group’s financial position is the most credible validation method available. It is also the most operationally demanding: it requires the finance team to run the close process twice, which is a significant burden on a team that is simultaneously learning the new system.
What Good Looks Like
An effective parallel run produces a formal reconciliation between the legacy system output and the new system output, at the account-entity-period level — not an aggregate comparison. A consolidated P&L that matches at the total revenue and total cost level may still contain account-level differences that are material in specific lines. The parallel run reconciliation must be performed at the level of detail that management reporting and statutory reporting require, not at a level of aggregation that makes differences invisible. The reconciliation is signed off by the finance director as evidence that the new system is producing the correct output before the legacy system is decommissioned.
What Organisations Get Wrong
The failure that renders a parallel run ineffective is reconciling at a level of aggregation that does not surface material differences. A consolidated revenue total that matches between legacy and new system is reassuring. The same match achieved by two equal-and-opposite account-level errors — one overstatement and one understatement that cancel out at the total — is misleading. Parallel run reconciliation must be performed at the lowest level of reporting detail that will be used operationally. If management accounts are produced at the cost-centre-account level, the parallel run reconciliation must be performed at the cost-centre-account level. Higher aggregation is not a shortcut; it is a risk that the parallel run was designed to eliminate.
How Loop Wise Solutions Approaches This
We design parallel run protocols that specify the reconciliation level in advance — before the parallel run begins — so that the finance team knows what they are reconciling and at what level. We include the parallel run reconciliation in the go-live readiness checklist: the parallel run is not complete until the signed-off reconciliation is in the programme documentation file. An unsigned parallel run reconciliation is not a completed validation; it is a demonstration that the new system was operated during the parallel period.
