Thanks for reaching out to the Community about undoing a reconcile.
The "undo" feature for reconciles is exclusive to the QuickBooks Online Accountants version. To undo a reconciliation, you must open the client's company file from QBOA (signed in as an Accountant user), then open the account, locate the reconciliation, and undo it.
Here are the steps:
In QuickBooks Online Accountant and signed in as an accountant user, select the client from the drop-down list on the Toolbelt to open the client's company file.
Select the Gear icon on the Toolbar.
Under Tools, select Reconcile.
On the Reconcile an account page, select History by account.
On the History by account page, select the Account and Report period to locate the reconciliation to undo.
From the Action column drop-down list, select Undo.
When prompted to confirm, select Yes.
In the final confirmation window, select Undo.
For more information about how to undo a reconcile, click here.
If you have any other questions about this feature, please feel free to reach out.