Glad to have you here in the Community, @mehtapsimsek-us.
I can share some information about deleting an account in QuickBooks Online.
Are you trying to delete a bank account from your Chart of Accounts? If so, you can only delete an account if it's not associated with any transactions in QuickBooks Online.
To do that:
However, if you've used the account to some of your transactions, then you can make the account inactive to ensure that your transactions will still show up on your reports.
Let me guide you how:
To get more information about this process, you may check out this article: How to delete an account or restore a deleted account.
Also, to learn more about dealing with accounts that are no longer use in QuickBooks Online, please refer to these articles:
In case you need further assistance with this process, feel free to get in touch with our Customer Care Team.
These resources should brighten up your day.
Let me know if you have any other questions with this concern or any QuickBooks related thing. I'm always here to lend a helping hand. Have a great day.