Two marks returns for one class code, for the same exam board have been created.
Two marks returns have been created where we only need one. Can the other be deleted?
No. But you can rename it. Open the marks return you don't want to use and edit the title in the textbox at the top, adding some indication that this return is not to be used. It may make things clearer and simpler if the naming convention for this scenario is agreed within your department. Then save the return.
You can later use this return for resits, if appropriate, again by renaming it appropriately within your naming convention, and editing it after the first board has passed.