> What happens if a bounty question is closed or deleted? / Why can't I vote to close or migrate a bounty question?
Bounty questions cannot be closed directly.
However, diamond moderators can clear bounties, which would effectively remove the bounty and clear its history. The bounty owner's reputation would be recalculated as if they had never placed that bounty. This would then allow it to be closed, migrated, or deleted like any other question. (source)