This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

Methodological Handbook: Strengthening tax compliance by implementing behavioural insights for revenue administration in Belgium, Austria, and Portugal

Understanding the complexities of human decision making has profound implications for tax compliance. Governments globally are adopting this approach to improve their services by simplifying information or changing the so called “choice architecture” faced by individuals making a decision. The ‘architecture’ refers to the way that a choice is presented to decision makers such as the taxpayers (e.g., whether or not tax returns utilise default options). Drawing on evidence from applications of BI in the area of tax compliance worldwide, this handbook explores how understanding human behaviour within its social context can offer innovative, cost-effective solutions to challenges in tax filing, payment, and accuracy.

This handbook aims to:

• Provide authorities and policymakers with a process which can be used to develop, test and implement behavioural interventions that improve tax compliance.
• Unpack the diversity of drivers of non-compliance in the context of taxation which have been identified in previous studies. This overview of drivers can be used as a starting point for authorities and policymakers to brainstorm about what drivers are relevant for the non-compliance issue(s) in their own countries. This identification is necessary before moving on to designing tailored measures. Furthermore, the handbook will provide an overview of previously tested behaviourally informed interventions by describing the mechanisms which were at their core. This overview is also expected to inspire users of this handbook when designing their interventions in their own countries.
• To help select the most appropriate research designs for each of the different stages involved in developing and evaluating measures using behavioural insights.

 

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This handbook is meant to be a toolbox for authorities and policymakers who are not behavioural scientists but who wish to use behavioural insights in their work. It is based on recent academic findings and supports a methodical and evidence-based application of behavioural insights in tax policies.

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

The analytical country reports provide a detailed diagnosis of the situations regarding tax compliance and the use of BI in the participating Member States, Austria, Belgium and Portugal, up to 2024. They draw on desk research, literature review, statistical analysis of anonymised tax records and compliance indicators, as well as workshops and interviews with tax administrators.

In each country, the institutional and regulatory context, the relevant tax obligations, the taxpayer journey, existing compliance challenges, past measures, and patterns and trends in compliance behaviour are examined. The reports also identify behavioural and practical barriers that may affect taxpayers’ ability or willingness to comply with existing tax provisions and highlight opportunities for targeted behavioural interventions to inform the subsequent stages of the project.

Overall, the analytical country reports aim to:

• Provide a structured diagnosis of tax compliance in each national context, including the relevant institutional framework, tax obligations, administrative procedures and existing BI capacity within the tax administrations.
• Map the taxpayer journey and identify critical barriers where taxpayers may face difficulties in understanding, declaring or paying their tax obligations in a timely manner, helping administrations understand where behavioural interventions may be most useful.
• Analyse compliance patterns and trends using available administrative data, identifying the main behavioural and practical drivers of non-compliance.

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

To support capacity building on behavioural insights, the JRC delivered training to tax administrations in the three countries. In April 2024 full-day introduction courses were provided to the operational teams (involved in the design and implementation of tax compliance measures) and connected services. These trainings introduced behavioural science concepts, methods and evidence, and focused on the identification of behavioural barriers in taxation processes and the design of behaviourally informed solutions (syllabus available below). They were delivered on-site in the respective national languages. In addition, 90-minute crash courses for management teams (teams responsible for strategic decision-making) highlighted the relevance of the approach, possible outcomes, and benefits to the administrations and taxpayers.

In November 2024 and January 2026, the JRC delivered additional advanced trainings to the tax administrations. These trainings were tailored to the specific needs of each tax administration and combined the expertise of the Behavioural Insights and the Design for Policy teams of the EU Policy Lab. In Belgium, the advanced module focused on statistical analysis methods for field trials. In Austria the focus was on deconstructing the ‘taxpayer journey’ to identify relevant decision and pain points for taxpayers where compliance may be negatively impacted. In Portugal, the focus was on empirical methods for testing the effectiveness of interventions, communication, intervention design, and methods for prototyping.

Overall, the trainings supported the tax administration in:

• Understanding the behavioural factors that lead to non-compliance and how to address them effectively
• Using experiments and evidence-based strategies to evaluate the impact of interventions as part of a culture of continuous improvement
• Improving communication with taxpayers through techniques that resonate with them
• Implementing low-cost interventions that can deliver significant results
• Building positive relationships with taxpayers by addressing their pain points and reducing frustration
• Developing creative and data-backed solutions to longstanding compliance challenges

EU Policy Lab blog post (09 April 2025): Making tax compliance easier: How to help taxpayers help you (if you’re a tax administration)

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

Three communication strategies were developed to support the overall effectiveness of the project by raising awareness of the project and its use of BI, promoting their acceptance and buy-in within the beneficiary tax administrations. They also supported the dissemination of relevant project outputs to key project participants, wider administrative staff, decision-makers, specialised stakeholders and, where relevant, the general public, helping them understand the potential of BI to enhance tax compliance and improve the efficiency of tax systems. In addition, they helped position the participating administrations as innovative, evidence-based and learning organisations committed to improving voluntary compliance and reducing administrative burden.

This deliverable combines an overall communication approach common to the three countries, with country-specific sections for Austria, Belgium and Portugal. First, the common approach identifies target audiences, roles and responsibilities, key communication channels, communication opportunities linked to project deliverables and proposes communication assets. These include internal updates, social media posts, short communication summaries, factsheets, webinars, internal presentations, and materials to support dissemination through the JRC knowledge database and final conference. The strategies also set out how communication should be organised across the project lifecycle, using each major deliverable as an opportunity to share evidence, lessons learned and practical examples.

The country-specific sections adapt the approach to the institutional context of each tax administration, identifying relevant internal and external stakeholders, such as project teams, management, communication departments, operational units, IT and data teams, other public authorities, international networks, academia and the general public. Additionally, these sections also map existing communication channels, such as intranet and SharePoint sites, internal newsletters, digital staff magazines, meetings, external events, websites and social media platforms used by the participating authorities in Austria, Belgium and Portugal.

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

This report presents the methodology and questionnaire developed for the survey on opinions, attitudes, trust levels and motivations for tax compliance in Austria, Belgium and Portugal. The survey collected data on behavioural, practical and socio-demographic factors influencing taxpayers’ ability and willingness to comply with their tax obligations. The survey explored taxpayers’ experiences along the tax journey, their knowledge and confidence in dealing with tax procedures, their perceptions of tax authorities and the fiscal system, and their motivations for compliant or non-compliant behaviour. Overall, this report supports the design of evidence-based interventions by identifying where taxpayers face difficulties, which behavioural drivers are most relevant, and how interventions can be better tailored to specific target groups and stages of the tax journey.

The survey was designed to build on the problem diagnosis carried out in the analytical country reports and the methodological guidance developed for this project, translating earlier assumptions about behavioural drivers of non-compliance into a structured quantitative research tool. The survey combined common questions posed across the three participating countries with country-specific questions adapted to the particular compliance issues identified in each national context. A key feature of the survey was the use of hypothetical scenarios adapted to each country’s specific compliance challenge, as a way to mitigate participant reluctance in disclosing non-compliant behaviour directly in the survey, while still allowing exploration of likely behavioural responses in realistic tax situations.

The survey was conducted online between the end of August and mid-October 2024, using representative samples of personal income tax taxpayers in Austria, Belgium and Portugal. In total, 6,039 responses were collected: 2,013 in Belgium, 2,008 in Austria and 2,018 in Portugal. Quotas and weighting were used to support representativeness in terms of gender, age, region and, in Belgium, language. The full questionnaire is also shared here in English.

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

This report presents a comparative analysis of the behavioural intervention trials implemented in Austria, Belgium and Portugal between April 2025 and February 2026. The trials were designed to test whether timely, targeted and behaviourally informed communication could improve tax compliance in real administrative settings.

Although the trials addressed different obligations and were adapted to each national context, they followed a common diagnostic and design process, thus providing a useful basis for comparing how similar behavioural tools performed across different administrative settings. The comparative report identifies several cross-country lessons, and also highlights the importance of reliable administrative data, clear target groups, robust evaluation methods and close coordination between behavioural, operational, IT and communication teams.

Overall, the comparative report aims to:

• Present the design, implementation and results of the behavioural trials conducted in Austria, Belgium and Portugal.
• Compare what worked across the three trials, explain how differences in context, compliance stage, target group and communication channel affected the results, and identify transferable lessons for the future use of BI in tax compliance.
• Provide practical guidance for designing, adapting and scaling behavioural interventions in other tax administrations.

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

The final conference, held in Brussels on 28 May 2026 in a hybrid format, marked the conclusion of the project and provided an opportunity to present its main activities, findings and lessons learned across Austria, Belgium and Portugal to a broad audience of stakeholders. The event brought together representatives of tax administrations, European institutions, international organisations and BI researchers to discuss how behavioural approaches can support tax compliance and improve tax administration performance. Building on the evidence generated throughout the project, the conference showcased the key outputs, with particular attention to the design, implementation and evaluation of behavioural interventions tested in real administrative settings. The discussions highlighted both the effectiveness of these interventions and the practical conditions required for their successful implementation.

This conference report provides a concise record of the event and its main takeaways. It includes the conference objectives, programme and agenda, an overview of the sessions and discussions, key messages on the use of BI in tax compliance, participation figures, and information on the range of stakeholders involved. The report also documents how the conference supported the dissemination of project results and the exchange of practical lessons between tax administrations and other organisations working in the field of taxation.

This publication is a deliverable under project “Strengthening tax compliance by implementing behavioural insights for revenue administrations in Belgium, Austria, and Portugal”. The project was funded by the European Union via the Technical Support Instrument, managed by the European Commission Reform and Investment Task Force (SG REFORM).

The brief summarises the project and describes its main activities. It also presents the three tax authorities and the needs of the project before jumping into the description of the methodology. After detailing each deliverable of the project, it goes through the main conclusions of the research findings and reflects on the impacts of the capacity building activities and the lasting organisational knowledge and resources created during project. Finally, it describes the expected impacts of the project for the tax authorities in terms of learning and capacity building based on the experiences from the project having researched, developed and tested different BI interventions.