GP provides a way to 'Reconcile' summary and detail data within the application. Each module has its own Reconcile utility. For instance, Tools>Utilities>Financial>Reconcile opens the Reconcile Financial Information window.
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Now, this Reconcile is not for reconciling a GL account to the subledger, i.e., Accounts Receivable to the AR Trial Balance. This Reconcile forces financial summary information, such as the monthly data in the Financial Summary Inquiry window, to equal the underlying detail.
Over time, some transactions don't post properly, data gets corrupted, etc, etc. This Reconcile fixes those data errors.
However, there is one aspect of this utility that you need to be aware of. Note that you can reconcile Open and History years. Be very careful that you don't reconcile a History year that contains only GL account balances. This might be the case where historical account balances were imported during an implementation because it was deemed unnecessary to import all the transaction detail. If you reconcile a History year in this scenario, it will zero out your account balances. Why? Because the Reconcile process, by design, forces the summary data to equal the detail transaction data. If there are no detail transactions - Reconcile will make the summary equal that!
Now, fortunately, GP presents a warning to this effect when you select a History year to reconcile. Heed the warning!!