@poppy1  Your question is kind of vague, so I'll throw out a few different answers, see if one sticks.

You cannot delete a bank account that is currently being used in transactions in QBO.

You technically can't delete a bank account, or any account at all, in QBO, per my understanding; you can only mark them 'inactive'.

You can change which bank is being used for a transaction, if you mistakenly chose the wrong bank account. If the transaction in question was already reconciled, you'll want to undo that first.

If you mean to ask if you can remove a bank from the list of bank accounts to import transactions from, I'unno. I mean, I'd hope that you could, but QBO is kind of a piece of garbage when it comes to a lot of things.