SOX requires the establishment of anonymous whistleblowing channels for public companies, but private companies are free to implement the channel(s) of their choosing. Although anonymous channels have long been considered a “best practice”, the evidence on their efficacy is mixed, creating confusion as to how private companies should proceed. Additionally, most studies comparing non-anonymous and anonymous channels have used a within-participants design, where both channels are available, limiting their ability to determine the incremental effectiveness of different whistleblowing systems. We find that offering either an anonymous channel or dual channels improves reporting intentions, relative to a non-anonymous channel, but primarily when tone at the top is weak. When tone at the top is strong, reporting intentions are not statistically different across the three systems. We also find no evidence that dual channels improve whistleblowing intentions relative to an anonymous channel, regardless of the tone at the top.