To build on what Happy said:
A payee does not necessarily equal a suspect. The specific facts of each situation will be used to determine who are your suspects and who are your victims.
That said, your initial posts leads me to believe that the scenario that is prompting your question relates to a customer of yours having their account compromised, and counterfeit checks being distributed. If that is the case, the payees are in all likelihood victims, who have received the checks as a result of a purported mystery shopping assignment, online romance, or some other common scam tactic. Even if each of these checks is under $1000, if the aggregate total of the counterfeit checks is $25,000 or more, then you have crossed the mandatory reporting threshold.