This report looks at effective e-service provision by tax administrations, summarising eight critical areas, and explores big data management and portals, as well as natural systems, in detail. It highlights key opportunities in these areas, looking at how these emerging technologies can be best used by tax administrations. It also provides practical examples of how tax administrations have begun to utilise these technologies and delivers a maturity matrix for the two areas to assist strategic and operational decision making by tax administrations. Finally, it sets out conclusions, recommendations and next steps. This report has been prepared by the Forum on Tax Administration's E-services and Digital Delivery Programme. The work was initiated by the FTA Bureau as part of its 2015/16 work programme and was led by the Federal Tax Service of Russia (FTS). With tax administrations clear that e-service options can improve taxpayer compliance levels and participation while at the same time lowering their cost of operation; but with available options many and varied, and with the cost of implementation high, the FTA has over the last five years provided a wide range of guidance in the deployment of effective e-services.