How to go back when I need to fix a correction that has been reconciled already?

Let's go to your Charts of Accounts to edit some transactions that already have been reconciled, Michele.

Changing anything but the amount and the account on any transaction won't change its reconciliation status. You'll need to undo the reconciled transactions to edit them, then manually reconcile them again.  I'll show you how.

1. Go to the Transactions tab on the left panel and select Chart of Accounts.
2. Locate the account holding the transaction. Then click Account history.
3. Select the transaction you want to unreconcile to expand the view.
4. In the checkmark column, repeatedly click the R status until it's blank or unreconciled. 
5. Click Edit to modify the entry, then Save and close.
6. Choose Yes in the confirmation window.
7. Select the box in the checkmark column until you see an R. This manually reconciles the transaction.
8. Repeat the steps for the rest of the transactions you want to edit.

Please know that editing reconciled transactions may result in discrepancies in your prior and subsequent reconciliations. I recommend consulting an accountant before performing the steps above to assist you in handling them. If you don't have one, you can connect with a ProAdvisor through this link: Accounting professionals.

Moreover, check out this guide for a detailed process when making corrections: Fix issues for accounts you've reconciled in the past in QuickBooks Online.

Furthermore, you can view, print, or export a reconciliation report in QuickBooks Online to verify that the entries recorded in the accounting system match the actual ones in bank statements.

If you have any additional concerns about reconciliation, please keep me in the loop by replying. Any questions about managing transactions are welcome as well. Stay safe!