Welcome to the Community, Andrea.
Let me guide you on modifying your last statement ending date for your reconciliation in your QuickBooks Online (QBO) account.
You can change the reconciliation ending date if you have not yet completed your reconciliation. First, let’s make sure that you have logged into your QBO. After that, you can follow the steps I’ll provide below.
1. Select Transactions at the left panel of your QBO account page, then choose Reconcile.
2. Click on the Resume reconciling tab.
3. Tap on Edit Info.
4. A panel at your right will pop up with your statement information.
5. Modify your date under the Ending date box.
6. Hit Save once done.
However, know that if you've already reconciled your transactions, you'll need to undo the reconciliation to correct the year-end date. I’d recommend reaching out to your accountant. They can undo the entire period at once using QuickBooks Online Accountant.
You can also check out this article that entails the guidelines on fixing issues when reconciling in QBO: Fix issues at the end of a reconciliation in QuickBooks Online.
If you need further assistance with modifying your ending date with your reconciliation in QBO. Don’t hesitate to leave a comment below. I’ll be here to assist you at any time.