Welcome and thanks for joining the Community. I can share some insights on how to reconcile your accounts in QuickBooks Online.
Before anything else, may I know if you're referring to correcting your ending balance? If so, you can do that by clicking the Edit info button in the Reconciliation page. Please see screenshot below:
However, if you need to fix the discrepancy with your beginning balance. You can undo the reconciliation manually then correct the difference afterward.
Go to the Gear icon.
Tap Chart of Accounts.
Find the account you want to review.
From the Action column, click View Register.
In the reconcile status column (indicated by a check mark), view the codes which show the status of the transaction:
C - Cleared
R - Reconciled
Blank - Not cleared or reconciled
Here's how it looks like in QBO:
Once done you can now update the balance. Please know that you can only edit the Beginning balance if it is your first time setting up the account or if there aren't any transactions yet. To get past the problem, follow the steps below:
Click the Gear icon.
Select the Account you want to reconcile.
Tap the "We can help you fix it" link on the beginning balance alert.
On the Reconciliation Discrepancy Report, verify which transactions are causing the difference in the Change Type column.
Once you identify the issue, you can correct them by creating adjusting entries or recreating the deleted transaction if any. Before making any corrections, I'd suggest consulting this with an accounting professional to get the best legal and accounting advice for this type of concern.
You can also check these related articles for the complete steps: