If you no longer use an account, you can mark it as inactive to prevent processing further transactions. You can't delete the bank account. 

You can't set a bank account to be inactive if it’s connected to a bank feed. Disconnect your bank feed first.

1. Go to Sole Trader.
2. From Banking select Actions on the relevant bank account.
3. Select Mark account as inactive. 
4. Confirm the action by selecting Mark as inactive on the popup message.
5. You can toggle between banks using the All, Active and Inactive buttons.