The States have auditors to audit state and local agencies.
But, I have never heard of a State where they audit the Voter Registration Rolls.
Why is that?
Most voters have telephones.
If the telephone service is terminated or if the phone moves out of state the voter registration could get cancelled if two do not forward mailings are not answered.
Do not forward registration reinstatement mailings might be sent at 30, 20 and 10 days before the registration window closes for the next election.