How can I delete a reconciled bank ststement so I can find an error and then run the reconcilation again?

It's my understanding that only a QuickBooks certified accountant has the ability to un-reconcile an account. That's not the way the situation is handled in the desktop app but I don't think there's an option for a regular user to delete a reconciled bank statement in the online version. 

Let me share information to undo reconciliation in QuickBooks Online, @attrue.

If you're currently utilizing QuickBooks Online Accountant, you can undo a reconciliation using the feature without going through the register and manually changing each transaction. You must unreconcile each transaction from the register if you're not utilizing QuickBooks Online Accountant. Below are some steps to undo reconciliation for both positions.

QuickBooks Online Accountant:

1. Go to the Accounting menu.
2. Select the Reconcile tab.
3. Click History by account.
4. Choose the account you want to reconcile and the date range from the dropdowns.
5. Find the reconciliation on the list.
6. Tap on View report to open the Reconciliation Report.
7. Review any discrepancies and changes your client wants to make.
8. When you’re ready, select the dropdown in the Action column, and then choose Undo.
9. Hit Yes and then Undo to confirm.

Non-accountant:

1. Go to the Accounting tab on the left panel.
2. Under Your Company, select Chart of Accounts.
3. Choose the account you’re working on, and click on View Register.
4. Select the transactions you want to unreconcile.
5. Keep clicking the R status until it shows blank or cleared (C).
6. Click on Save.
7. Choose Yes in the confirmation window.

I also want to provide details regarding how to settle disagreements after reconciling. To review this data, Check out Fix issues at the end of a reconciliation in the QuickBooks Online article.

For additional details about undoing reconciles and individual transactions, check out the help articles I've included below.

• Undo or remove transactions from reconciliations in QuickBooks Online 
• Undo a client's reconciliation in QuickBooks Online

Let me know if you have additional questions about unreconciling in QuickBooks Online. I'm always here to help. Have a great day.