Maturity models are a relatively common tool, often used on a self-assessment basis, to help organisations understand their current level of capability in a particular functional, strategic or organisational area. In addition, maturity models, through the setting out of different levels and descriptors of maturity, are intended to provide a common understanding of the type of changes that would be likely to enable an organisation to reach a higher level of maturity over time.The OECD Forum on Tax Administration (FTA) first developed a maturity model in 2016 in order to assess digital maturity in the two areas of natural systems/portals and big data. The digital maturity model was introduced in the OECD report Technologies for Better Tax Administration (OECD, 2016). Building on this, work began in 2018 to develop a set of stand-alone maturity models covering both functional areas of tax administration, such as auditing and human resource management, as well as more specialised areas such as enterprise risk management, analytics and the measurement and minimisation of compliance burdens. The maturity model contained in this report, which is intended to be the first in a series of published FTA maturity models, covers the functional area of tax debt management. Tax debt management is a large function, employing around 10 percent of tax administration with outstanding collectible tax debt across the FTA of around EUR 820 billion (OECD, 2019 ). There are, though, significant variations in tax debt management performance and administrations also have different powers and tools available to them to deal with tax debt, as shown in Chapter 3 of the Tax Administration 2019 report (OECD, 2019). Against this background, the aim of the tax debt management maturity model is: •To allow tax administrations to self -assess through internal discussions as to where they see themselves as regards maturity in various aspects of tax debt management.• To provide debt management staff as well senior leadership of the tax administration with a good oversight of the level of maturity based on input from other stakeholders across the organisation. This can help in deciding strategy and identifying areas for further improvement, including where that needs to be supported by the actions of other parts of the tax administration. • To allow tax administrations to compare where they sit compared to their peers. The results of the initial piloting of the model by twenty-one tax administrations (including some non-FTA members) were analysed by the OECD FTA Secretariat. A “heat map” contained in this report shows the reported maturity of different administrations, on an anonym ous basis. This report consists of four parts: • Chapter 1: Using the debt management maturity model. This provides an overview of the model and an explanation of how to use the model, including how to get the most out of discussions within the tax administration. • Chapter 2: Results of pilot self-assessments. This chapter sets out the anonymised results of the pilot undertaken to refine the maturity mode Chapter 3: The full tax debt management maturity model. The chapter contains the model which can be used by tax administrations for self-assessment purposes and, following anonymised collation of results, for the purposes of international comparisons.• The Annex contains a record sheet for internal purposes, including to inform repeat use of the model from time to time, and for anonymised comparison purposes when submitted to the Secretariat. (This annex and the tax debt management maturity model are both available in word version on the FTA website.) The tax debt management maturity model was developed by an advisory group of tax administrations from Belgium, Canada, Hungary, Norway, Spain and Singapore. It has also benefited from discussions with the members of the FTA Tax Debt Management Network, chaired by the General Administration for Collec tion and Recovery under the Belgian FPS Finance, and from a pilot undertaken by a wide range of FTA members and some non-members.