Important: If you turned on iCloud Drive for Numbers (in System Preferences on your Mac), deleting a spreadsheet from iCloud Drive removes it from iCloud and from all other devices and Mac computers that use the same Apple ID.
If you don't know where the spreadsheet is, locate it first.
Select the spreadsheet, then do one of the following:
Drag the spreadsheet to the Trash icon in the Dock.
Press Command-Delete on the keyboard.
To empty the Trash (and permanently remove the spreadsheet from your computer), click and hold the Trash icon in the Dock, then choose Empty Trash.
If you're working on a new spreadsheet that hasn’t been named or saved yet, and you don't want to keep it, close the spreadsheet, then click Delete in the Save dialog that appears.
If you open an existing spreadsheet, edit it, then decide you don’t want to keep any of your changes, you can revert the spreadsheet to how it was when you opened it.