Tax Controversy 2026

A Global Overview of Tax Controversy in 2026

Uncertain times continue

Unpredictability still reigns in the tax controversy landscape: once introduced by Brexit, coronavirus and numerous wars, the plot now seems to thicken following the imposition of tariffs, subsequent market retaliation, and the risks and new disruptions for global supply chains, namely as oil prices hit new highs (and sudden lows, given their immense volatility) in the aftermath of Trump’s recent armed incursions in Venezuela and the Middle East. All these have had a clear impact on the global economy and financial markets, with global M&A activity slowing down. With all this in mind, the climate is likely to be stressed and to be reflected in states’ budgets and in the legal environment. All these events and circumstances will have a huge impact on budgets, on taxes and likely on controversies in the years to come, given the additional stress put on the different players.

In order to combat the COVID-19 pandemic, governments supported individuals and companies in need with measures to postpone tax payments or embrace flexible approaches towards compliance with specific obligations. This is now over. However, public spending has since increased substantially, and the various wars and conflicts – and now the tariffs wars – have increased pressure on budgets. Moreover, one cannot ignore that not long ago a new set of hard and soft law instruments was created to target several behaviours. The situation is naturally different in each country, but some fear that new taxes will be created and, at the same time, predict that the tax authorities will be inclined to be stricter and/or carry out more targeted audits, although the selection of taxpayers by the tax authorities seems to be undisclosed in many countries; as the Belgium chapter of this guide asserts, “the BEPS recommendations and the EU’s recent measures (…) as well as recent ECJ case law on abuse, are translating into tax disputes…” and, in relation to audits, makes clear that “their (tax authorities) algorithms are a closely held secret”. The Poland chapter also calls our attention to the fact that usage of such data results in “intensifying its (tax authorities) scrutiny of the largest groups”.

More than ever, the management and control of tax risks are primary goals for both tax authorities and taxpayers. For the former, it is disastrous if the State is unable to collect the expected level of revenue. For the latter, tax is a significant cost for business, and an incorrect estimate can jeopardise a company’s level of profitability and damage its reputation, not to mention cause egregious disadvantages and losses. However, it is now almost certain that, in the short term, debt and public expenses will increase while tax collection levels will drop due to the economic contraction.

It might be debatable whether taxes are a prime mover of history, as some have argued, but one cannot ignore facts. The US experience after the 2008 crisis, when both tax authorities and multinational enterprises (MNEs) were in need of revenue and neither were prepared to compromise easily, should be borne in mind. Currently, it seems that the IRS, as well as several other tax authorities, is focusing more of its attention on international tax issues and, more specifically, transfer pricing. As the Germany chapter puts it, “[i]n recent years, international tax audits in Europe have become increasingly aggressive, leading to a growing number of tax disputes”. However, the USA chapters call the reader’s attention to several other relevant areas as well as to taxpayers that may have a greater likelihood of audit, and even to the “increased emphasis on expanding the use of Alternative Dispute Mechanisms (ADR) programmes”.

Owing to these risks, several authors – including in south European countries such as Greece or Portugal – direct special attention to the conclusion of advance pricing agreements (APAs). However, this is a novelty for certain countries (such as Brazil), mostly due to how recent specific legislation is that covers such a possibility. As the Brazil chapter highlights, “[a]lthough still in the process of regulatory development, APAs are expected to function as preventative instruments aimed at reducing future disputes rather than resolving existing ones”.

Anticipated Increase in Tax Litigation

Inevitably, no one can anticipate and eliminate entirely all adverse situations that might lead to disputes. Although disagreements may emerge suddenly and in relation to all types of taxes, the majority of chapters in this guide refer to the many international, complex and controversial substantive tax matters around the BEPS Recommendations, including the adoption of Pillar Two and the legislation created thereafter, the Multilateral Instrument (MLI), digital taxation and the use of the General Anti-Abuse Rule (GAAR) to challenge cross-border transactions, although many contributors cannot ascertain whether these have contributed to an increase in the level of tax controversies (see Canada). Many authors are already anticipating more litigation (see Belgium, Portugal). The same expectation exists with respect to the impact of the EU Mandatory Disclosure Directive (DAC 6), and many jurisdictions within the EU have mentioned this possibility.

Several chapters suggest that the amount of new legislation everywhere and the appearance of new and open concepts applied worldwide in the context of states struggling for financial resources create an expectation of increased litigation. Although the EU member states have already implemented EU Directive 2022/2523, it is yet to be seen how domestic legislation implementing Pillar Two might result in an increase or a mitigation of litigation (and whether Pillar One becomes adopted or not).

The recent new international instruments – such as the several packages involving the collection of more data and exchange of information between tax authorities, DAC 6 and the MLI – are still expected to have a significant impact on how anti-abuse rules will be applied. All together though, these will probably contribute to an increase in controversies and litigation.

The tax authorities of each jurisdiction might have different perspectives on and approaches to combating non-compliance with tax obligations or tax avoidance. Nevertheless, they are all undoubtedly better equipped and prepared, with substantially more information at their disposal about taxpayers as well as their own activity, and are much more integrated internationally, as several chapters mention. Curiously, this appraisal is not unanimous, with the Italian chapter admitting that, due to the incremental risks, taxpayers are likely to assume a more conservative approach in carrying out their business activities, which may contribute to a reduction in litigation over time.

Despite agreeing with this view towards taxpayers’ behaviour, tax authorities are placing increasing pressure on collecting taxes, and the borderlines and grey zones continue to subsist in many areas provoked by new legislation, open legal concepts, different interpretations, etc. Therefore, only time will tell whether litigation does or does not increase.

Audit Strategy and the Road Ahead

When perusing the chapters in this guide, it is noticeable that taxpayers – even MNEs and high net worth individuals – are often caught in the crossfire created by the competition between states for capital and investment, and suffer from a changing and uncertain compliance landscape. It is therefore extremely valuable to know how to expect, prepare for and manage possible audits or to verify whether it is possible to eliminate or mitigate tax risks, either before or during a specific controversy.

This guide presents an excellent overview of the main aspects of the tax controversies that are common and distinct in more than 30 very different jurisdictions. It provides a highly interesting global analysis of trends, including:

• the origin and causes of tax controversies;
• the continuous efforts to combat tax avoidance and evasion;
• the means to mitigate and manage tax risks and to stay up-to-date with the best ways to settle cases; and
• the strategies to employ in the context of administrative or judicial litigation.

The reader will also be able to gather comparative information on all phases of tax litigation in each jurisdiction, in either domestic or cross-border disputes, as well as an idea of costs and statistics in the area of tax litigation, including the number of cases and the likelihood of a successful outcome for the tax authorities or the taxpayers.

International Tax Authority Co-Operation

It is clear from all the chapters in this guide that tax authorities are collecting more and more information on taxpayers and on their businesses and cross-border activities, either through exchanges of information and mutual assistance, country-by-country (CbC) reports, the Common Reporting Standard (CRS) or other mechanisms or groups (eg, the Joint International Taskforce on Shared Intelligence and Collaboration). The reporting obligations contained in DAC 6 will also soon be automatically exchanged in the EU.

Whether one is in Italy, China, Brazil or the USA, tax authorities now know more than in previous years. Given the specific circumstances, culture and approaches in each jurisdiction, there is no unanimity as to whether this will lead to an increase in tax controversies, but several assertions and hints suggest it will, at least in some countries. Above all, however, taxpayers may expect more prepared tax authorities, with more information and well-defined targets, meaning that scrutiny and perceived abuses or avoidance techniques will be systematically tackled. The USA chapter emphasises these aspects clearly, noting that the IRS has expanded its use of ADR programme – which underlines the fact that, despite a rapidly shifting policy environment, this remains a time of great uncertainty in the realm of tax controversy.

Litigation and Tax Authority Approaches

According to the chapters in this guide, some tax authorities are seemingly investing in minimising tax disputes, helping taxpayers effectively via direct contact, through tax rulings or through the use of ADR mechanisms. This open approach appears to be paying off, considering that, when litigation occurs, the tax authorities claim a higher success rate before the tax tribunals or higher courts, as emphasised by a few contributors.

In countries where the tax authorities seem more reluctant to invest in assisting taxpayers dealing with complex legislation and ambiguous matters, additional tax assessments have grown significantly, which also gives rise to an increase in the number of controversies. Unsurprisingly, this reflects negatively on how investors evaluate the “tax element” when researching the different aspects of doing business in that specific jurisdiction (the case of Brazil is one example). In these countries, taxpayers can usually prevail more often. The Brazil chapter further notes that the country is currently undergoing a comprehensive VAT reform, consolidating multiple indirect taxes into a dual system (CBS and IBS), with a transitional phase running until 2032. This fundamental restructuring is expected to generate a new wave of disputes as taxpayers and authorities adapt to the new framework, adding yet another layer of complexity to an already litigious environment.

The China chapter – which also highlights the entry into force on 1 January 2026 of a new VAT Law replacing rules that had stood for nearly 30 years – emphasises the relevance of “smart tax (AI)” systems such as the fourth phase of the Golden Tax (including a comprehensive digital electronic invoice system), which can carry out comprehensive data management for enterprises and individual taxpayers. The conclusion is that “tax authorities monitor taxpayers’ tax risks in a timely manner through intelligent analysis of big data”.

Meanwhile, in some other countries, tax legislation and the tax authorities’ approach seem to occupy a middle ground between the types of patterns described above. Statistics regarding the success of the tax authorities in litigation seem to be in line with this, and it is particularly interesting to analyse the statistics in each country and the reasons presented by the authors.

Efficient ADR mechanisms may also be very helpful in preventing/reducing disputes or at least resolving them quickly, as shown by the Portuguese domestic arbitration system. The administrative attitude and the taxpayer culture still seem to be the crucial elements, however – ADR mechanisms may not be sufficient without a willingness on the part of both the authorities and the taxpayers to work collaboratively, and with reasonable alacrity.

Criminal Tax Controversies

This guide also illustrates the way tensions that may be avoided as they arise and may evolve from tax audits up to the higher tribunals, either through administrative and civil discussions where anti-avoidance rules (including transfer pricing) still play an important role, or in the context of tax evasion or fraud – involving, for example, dishonest conduct and false accounting – when such matters will usually be treated as crimes, and where the proceedings and the investigations are conceptually separate and evolve independently. The guide explains the differences, the possible interactions between tax assessments and tax infringements, and the possibilities to reduce fines and/or to initiate and conclude settlements. In some countries, there is an increased risk of criminal liability, not only for the taxpayers themselves but also for the so-called facilitators. Moreover, some situations start being deeply scrutinised as a crime. The Netherlands chapter mentions that “[t]he Fiscal Intelligence and Investigation Service (…) is also focusing on investigating complex forms of financial and fiscal crime”, such as “financial fraud, money laundering, cybercrime and corruption”.

In addition, it seems that there is a trend for more collaboration between tax and criminal bodies, including judicial authorities, through specialised joint investigation teams, as noted in the Belgium or the Portugal chapters, for example. The Belgium chapter stresses that “[t]wice a year, the tax authorities and the College of the General Prosecutors hold a strategic meeting to determine priorities”. Also, the UK chapter notes that “310 prosecutions were brought as a result of HMRC criminal investigations (although this is lower than the prosecutions brought in the prior year, of 344). This secured 281 convictions with a success rate of 91% in court”. This trend, with the same or different strategies, has also been pointed out in several other reports (namely Portugal).

Finally, one cannot ignore that a new criminal trend seems to be emerging involving many other persons besides the taxpayers themselves.

Litigation Strategy

The reader is guided by each contributor to this guide through different geographies along the administrative and judicial routes, from the first to the final stages (that is, taking into account administrative hierarchical or judicial appeals), considering deadlines, intricate proceedings, and rules and principles that reveal how disputes may be settled in the most appropriate manner.

Despite the existence of absolutely different procedural rules and ways to settle tax disputes, there are several important common features that contribute to taxpayers’ best interests, which are stressed by the majority of authors. These include:

• the importance of being prepared before an audit has even started and of being assisted by a legal adviser from the first hour;
• the need to be fully conversant with all the relevant facts around the potential controversy, and to evaluate the risks and associated contingencies in order to minimise them;
• supporting the facts and bolstering the substance of the case, disclosing documentation and engaging expert assistance, or any other necessary support;
• verifying whether the dispute may be narrowed, by either settling or abandoning any of the issues, but making wise use of all procedural and material rights; and
• the importance of an awareness of previous case law, even in civil law jurisdictions where precedent does not have the same strength as in common law systems – this importance increases with the need to know international jurisprudence from the ECJ or the ECHR and to be aware of comparative jurisprudence or doctrine.

Naturally, in-depth analysis of a case, its facts and the applicable rules of law are crucial to mastering tailor-made strategies for individual cases, as this guide repeatedly emphasises. The reader will certainly understand that, in spite of globalisation and similar concepts/substantive tax issues (such as transfer pricing matters, hybrid mismatches, recharacterisation issues or cross-border disputes after BEPS) or procedural rules and principles, the way that disputes may best be settled in each country is still part of the expertise and art of practitioners in the respective jurisdictions.

International Issues

The different chapters also emphasise the use of domestic or international tools – such as the mutual agreement procedure – to solve cross-border disputes, indicating how they usually interact. Some of the chapters allude to the MLI, considering that it is already in force in several countries, and provide an idea of the crucial matters. 

A brief note is due to a withholding tax dispute relating to the source of royalty income under the Korea-US Tax Treaty that had been ongoing since 1992: the Korea chapter states that “the Korean Supreme Court departed from its prior precedents and held that, even where the patent itself is not registered in Korea, royalties may constitute Korean-source income if the underlying patented technology is used in Korea (eg, in manufacturing or sales)”.

The issue of state aid disputes involving taxes naturally does not apply to all jurisdictions, but within the EU it is a hot topic to which member states and taxpayers should pay great attention for its practical impact on sensitive matters (where exemptions and incentives could be withdrawn, and turnaround in the recovery of taxes and interest is a real possibility), as some of the EU chapters show.

It is also interesting to observe that the GAAR and Specific Anti-Abuse Rule (SAAR) application in a treaty context have already been challenged in several court cases. However, the majority of chapters choose to stress confidence in their compatibility, as tax authorities and states have repeatedly invoked (along with the OECD Model Tax Convention commentaries), suggesting that taxpayers should – if not must – adopt conservative approaches to exploiting double taxation treaty opportunities. The MLI also contributes to changing the situation, particularly considering the “saving clause” (Article 11).

The fight for income from international taxation ignites intense discussion, not only among taxpayers but also among different tax authorities and states. The appearance of so many new tools and weapons to combat tax avoidance allows us to predict that tax disputes will increase, unless great investment is made in assisting taxpayers on a daily basis and in creating ADR mechanisms. Ironically, it seems that, at the same time that an avalanche of new measures has been created to combat taxpayers’ abuses (BEPS, DAC 6, etc), states have felt the need to create quick arbitration mechanisms to settle tax disputes between themselves (eg, the MLI and the EU Arbitration Directive).

Conclusion

Authors from several jurisdictions predict stricter audits and additional tax assessments in the near future, and possibly even more taxes. Once the ongoing geopolitical conflicts recede (although predictions of their absolute conclusion are still pure speculation at this point) and the tariffs wars terminate, the authorities will have to consider the approach to “recovery”, considering that states will want to preserve their business sectors for long-term economic growth. Clearly, given the current status quo, taxpayers should be more proactive in their internal audits and the analysis and management of their tax risks.

Considering that every move takes time and that the state of the art in each jurisdiction is at a different stage of development, the present guide is an excellent tool for professionals (tax lawyers, barristers and in-house lawyers, but also company CFOs and members of their departments, tax consultants, judges or other professionals), providing a compass with which to find the right path forward when preparing and handling a tax audit or controversy, to assist either in managing a good settlement or, if this proves unworkable, in conducting a successful dispute.