Online taxation systems have been among the most successful of e-government applications both in terms of citizen take-up and savings to the taxpayer. Understanding the factors that lead to high take-up is of potential interest to other public sector online service providers. This paper examines the quality of the online service provided by the Irish Revenue Commissioners' tax filing and collection system, Revenue Online Service (ROS). A modified version of the recently operationalized E-S-QUAL instrument is used to examine online service quality from the point of view of the citizens and tax practitioners who use this eGovernment system. The findings show that efficiency and ease of completion are the dimensions of website service quality that most influence ROS users' perceptions of value and convenience as well as their intentions to use and recommend the website to their peers. The practical implications of these findings include the fact that providers of public sector e-services should concentrate on communicating the functionality of their e-services. In addition, they should focus on reducing citizen concerns regarding misuse or mismanagement of personal data. © 2010 Operational Research Society Ltd. All rights reserved.