To remove an opportunity from Tenders.Net you will need to open up the Manage Tenders list relevant to the tender status, whether Incomplete, Delayed or Current. You cannot delete Closed or Awarded tenders.
Each listed tender that can be deleted will have the Delete icon in the Actions field. Click on this and you will be asked to confirm the action before the tender will be removed.
When a tender is deleted it is removed immediately and this action cannot be undone. You will need to entirely re-advertise an opportunity that you have deleted.