I am trying to undo the changes in a bank reconciliation. But because of rules that I have created, I cannot undo the changes I've made. How do I cancel these rules?

Welcome to the Community, @geoffandros.

Cancelling or deleting bank rules in QuickBooks Online (QBO) is pretty quick and easy. Please refer to these steps:

1. In QBO, go to the Banking menu at the left pane to get to the Banking page.
2. Click the Rules tab, then place a checkmark on the rules to be deleted.
3. Select the Batch actions drop-down and pick Delete. 

Once done, you can now proceed with undoing the changes in the previous reconciliation. For more information, please refer to these articles:

• Find previous reconciled adjustments.
• Reconcile an account in QuickBooks Online.

In case you want to set and use bank rules again, consider checking out this article for further guidance: How to set and use banking rules for downloaded transactions.

Please know that I'm only a post away if you have any other issues or concerns. I'll be more than willing to assist. Enjoy the rest of the weekend!