Hello, Saeed.
When you disconnect a bank account in QuickBooks, it doesn't get deleted, so its old balance remains on your Balance Sheet. Adding a new bank account creates a second, separate record. This is why you see both accounts, resulting in a duplicate entry.
To avoid duplication on your balance sheet in QuickBooks Online, we can merge the old, disconnected account into the new active account, combining the transactions and data from the old account into the new one.
Before merging the account, you must first reconcile the transactions in your old account. After that, take note of the Account Name, Account Type, and Detail Type of the old account. These must match the new account to show the Merge option. Once done, here's how to merge both accounts.
- Head to the Gear icon in the upper-right corner of your screen.
- Select Chart of Accounts.
- Choose the bank account you want to merge and click Edit in the Actions column.
- Make sure the Account Name, Account Type, and Detail Type match the new account exactly.
- Click Save and Close.
- QuickBooks will recognize the duplicate name and display a warning message asking, You already have an account with that name. Would you like to merge the two?
- Select Yes, merge accounts.

Any other questions? Drop them below.