You can always delete a quotation. But it can always be easy to save a quote for a later date. It is a kind of reference work on your administration, for example to be able to view prices that you have previously used. So keep in mind that it is not customary to delete quotations. A quotation cannot be deleted if it has been sent, accepted or converted to an order.
If you still want to delete, select the quotation you want to delete in the overview. Then click on delete. The quotation with all associated information will now be removed.