To undo a reconcile within your QuickBooks Online, your accountant will have to use their QuickBooks Online accountant account. They can use these steps below to successfully undo the reconcile:
Go to the Accounting menu.
Tap the Reconcile tab.
Select History by account.
Pick the account you want to reconcile and date range from the dropdowns.
Find the reconciliation on the list.
Click View report to open the Reconciliation Report.
Review any discrepancies and changes your client wants to make.
When you’re ready, press the dropdown ▼ in the Action column, and then choose Undo.