15 C.F.R. § 1500.105
(a) The agent(s) shall accept all ballots cast. However, if an agent determines a need for additional review for any reason, the agent shall endorse above the voter's signature on the ballot with a statement to the effect that the ballot needs additional scrutiny. The agent will attach to the ballot information regarding the reasons for additional review, the results of any investigations made with respect to the review, and the final disposition of the review. Agents will not count ballots found to be invalid or late, a non-exhaustive list of examples include: