Before merging accounts inside QuickBooks Online (QBO), know that if both account registers contain transactions, you may need to delete the transaction with the most recent date before merging. The older transaction becomes the opening balance of the newly merged account. You can visit this page to learn more about the process:
Merge duplicate accounts, customers, and vendors in QuickBooks Online.
Furthermore, we recommend checking these articles to help you manage bank transactions and reconcile an account inside QuickBooks:
As always, we'll be around if you need assistance managing bank accounts or transactions inside QuickBooks. Don't hesitate to comment so we can provide you with the necessary steps to resolve your concern. Have a good one.