invalidator
1. [ noun ] (work) an official who can invalidate or nullify
Synonyms: voider nullifier
Examples:

"my bank check was voided and I wanted to know who the invalidator was"

Related terms: official invalidate
Similar spelling:   invalidate
  invalidated
  invalidation
  invalidating
  invalidity
  invalidism
  invalidness
  infelicitous
  inapplicable
  in_flight