The couple has to obtain a marriage license from their local courthouse, which they must provide to you at the time of the ceremony. The fee is $93.50, and the couple must go in person. Once the license is issued, there is a 3-day waiting period before it can be used. After the waiting period, the license must be given to the notary; the notary performs the ceremony and completes the “certificate” portion of the license and then mails it back to the court. (The couple can not return the license to the courthouse themselves, despite what the court clerks may tell the couple – it’s against the law).
Of course, as with all notarial acts, the notary will also have to see the bride and groom’s photo ID before performing the ceremony.