We assess the effectiveness of accountability systems relying on patient reporting in the Kenyan health sector. We evaluate patients' willingness to file complaints on service providers, and providers' responsiveness to the possibility of receiving such complaints. We contrast reporting systems where complaints have no direct consequences on providers, such as standard complaint boxes, and reporting systems where complaints lead to either monetary penalties or non-monetary consequences, in the form of peer shaming. We employ a specially designed laboratory-in-the-field experiment involving randomly selected providers and patients from public and private health centers in Nairobi. We find that: 1) disclosing patients' complaints to providers' Health services, bottom-up accountability, patient reporting, peer shaming.professional peers is equally or more effective than imposing monetary penalties based on patients' complaints; 2) the possibility of retaliation against patients does not annul the effectiveness of reporting systems relying on peer shaming; 3) associating tangible consequences to complaints slightly lowers patients' willingness to file such complaints, mainly due to the existence of personal relationships with providers. Overall, our findings support the implementation of citizen reporting systems that leverage peer pressure and reputational concerns.