I removed a wood-burning stove and cut through the double-lined metal chimney flue in the attic. In the short term I jammed some insulation in the metal liner and left the rest of the chimney with the existing cap (see pic) on the roof. The top has a removable cap like this (duct tape was a short-term fix to stop airflow):
Can I just cap the top off and leave the bottom where I've cut it?
Whatever I do needs to pass a home inspection because we are selling the house soon.