How do i remove a bank account that is no longer in use?

Hey user41107, 

You can disconnect the account if there is a live connection by going to Banking > Pencil icon on bank account > Edit account info > Disconnect this account on save.

You will then be able to make the bank account inactive by going to Accounting > Chart of Accounts > Make inactive on the action drop-down. If there is a balance in the account a message will appear notifying QuickBooks will create an adjusting transaction for the balance amount.