The Tax Administration Series (TAS) examines the fundamental elements of modern tax administration systems by using an extensive data set, analysis and country examples to highlight key trends, recent innovations and good practices. 

First launched in 2004, the main purpose of the series is to share information that will facilitate dialogue among tax officials and other stakeholders on important tax administration issues, like identifying opportunities to improve the design and administration of their systems both individually and collectively.

The underlying data set, which is publicly accessible, comes from the International Survey on Revenue Administration (ISORA). This is a cooperation between four partner organisations: the Inter-American Center of Tax Administrations (CIAT), the International Monetary Fund (IMF), the Intra-European Organisation of Tax Administrations (IOTA) and the OECD, and is also supported by the Asian Development Bank (ADB). 

To support the progress of digitalisation and digital transformation of tax administrations globally, the web-based Inventory of Tax Technology Initiatives (ITTI) was developed with the assistance of regional tax organisations and as well as the IMF and the ADB.

ITTI, which will be updated in regular intervals, looks at both leading technology tools and digitalisation solutions implemented by tax administrations as well as approaches that will help to advance digital transformation. In addition to providing a snapshot of which administrations have adopted particular technology tools or approaches, the inventory also contains links to case studies provided by participating tax administrations to provide a more in-depth look at particular implementation solutions.

The Forum on Tax Administration Maturity Model Series sets out descriptions of capabilities and performance in particular functions or sets of activities carried out by tax administrations across five discrete maturity levels. The tools are available for tax administrations globally to use in order to self-assess their current level of maturity and to facilitate consideration of future strategic priorities, depending on each administration's unique circumstances and priorities.

The self-assessment results received from tax administrations are included in the relevant publication in the form of a heat map, as illustrated here for the digital transformation maturity model. The results are anonymous to encourage open and frank dialogue during the self-assessment.