Welcome to the Community, @ameen1. I'm here to ensure you'll be able to undo a bank reconciliation.
Beforehand, please know that the option to undo a reconciliation is exclusive for QuickBooks Online Accountant users. Thus, we can remove an individual transaction from a completed reconciliation from the Chart of Accounts.
Before doing so, I'd recommend reaching out to your accountant before making the changes to ensure the accuracy of your books.
Once you're ready to undo, here's how:
From the Bookkeeping menu, select Chart of accounts.
Find the account and select Account history.
Search the transaction you want to unreconcile.
Go to the check column. If the transaction is reconciled, you’ll see an “R.”
Select the checkbox. It changes the letter in the box. Keep selecting it until it is blank to remove the transaction from the reconciliation.
For future reference, here are some additional resources to guide you through managing your reconciled transactions and fixing issues you encounter along the way: