The global billionaire tax and the ATI
While humanity's collective wealth and productivity have reached unprecedented levels, the distribution of these gains remains deeply skewed. The challenges of effectively taxing ultra-high-net-worth individuals (UHNWIs) are increasingly drawing the attention of policymakers worldwide. Based on the proposal of a global minimum on UHNWIs developed by Brazil during its G20 presidency, the ATI commissioned a study to analyse taxable assets and potential revenues across its partner countries.
During this webinar, held on 22 May 2025, Christoph Trautvetter, coordinator of Tax Justice Network Germany and author of the study, shared the study's key findings, while Atty. Jocet Concisa P. Dita, Deputy Executive Director of the National Tax Research Center of the Philippines, offered insights from the country's perspective on the proposal. Organised by the ATI, the event provided a platform for ATI members to discuss the study's implications and engage in dialogue based on the speakers' presentations.
The webinar started with Christoph Trautvetter’s presentation. He explained that the study’s methodology builds on the approach proposed by Zucman, beginning with estimating the taxable wealth and potential revenue, followed by deducting the income taxes already paid by these taxpayers, and finally calculating the effective tax rates that would result from the billionaire tax. While Zucman’s study relied primarily on the Forbes billionaire list and estimated the impacts on six OECD countries, the ATI study focused on selected partner countries and included additional rich lists. In the lack of detailed tax data, for step two, Trautvetter accounted for regular tax rates of profits accumulated in companies to capture the baseline taxation burden. In the final step, while Zucman estimated the returns derived from Forbes list, the ATI study used individual examples of countries with good data availability to make the general revenue estimations.
The findings revealed that the potential revenues in ATI countries can reach up to $16 billion. This corresponds to 0.23% of GDP and 0.9% of total tax revenue, which is comparable to the figures for OECD countries with wealth taxes. The author highlighted that many ATI countries currently tax capital income at very low rates, or not at all, creating imbalances that a global minimum tax could help correct. He also noted that billionaires often avoid paying taxes on capital income by keeping profits within their companies, and in some countries, such as Brazil and Pakistan, there is little effort to tax it. The presentation concluded with a call for improved data, more research on HNWIs, and stronger national measures to implement effective taxation.
In the following, Jocet Dita brought the Philippines' perspective on the study. Marked by persistent inequality, the country has seen a significant concentration of wealth among its richest individuals in the last decade. In 2025, 15 billionaires held a combined wealth of USD 53.7 billion and the 9 richest Filipinos have more wealth than the bottom half of the population. Given this context, the nation has been discussing proposals for taxing the wealthy, including a “super-rich” tax and a luxury tax, which could collectively yield over USD 4.5 billion annually from the wealthiest Filipinos alone. However, there are still some reservations on the implementation of a billionaire’s tax. The arguments against this taxation centre around potential capital flight, the already existing wealth taxes, and their high administrative costs.
In the Q&A session at the end of the webinar, participants engaged in a lively discussion on the risks of capital flight and the feasibility of implementing a global minimum tax on UHNWIs. Markus Paffhausen from the ATI Secretariat raised concerns about whether there is substantial evidence to support worries about capital flight. Christoph Trautvetter responded by noting that in Germany, where a wealth tax has existed until 1997, there is little evidence of significant asset relocation abroad; billionaires find it expensive and undesirable to move their assets and tend to invest profits elsewhere while retaining ownership. Quentin Parrinello from the European Tax Observatory agreed, adding that while there is some impact—around 1% or 2%—the overall effect is minimal. He suggested that improved information sharing between tax administrations and creative national solutions could help address offshore wealth. Jocet Dita echoed these sentiments from the Philippines, saying that despite persistent fears, there is no concrete evidence that a wealth tax would drive capital flight.
The discussion also turned to the challenges of implementing such a tax, particularly in developing countries. One of the participants asked about the political economy and administrative hurdles in implementing these taxes. Jocet Dita identified the absence of a comprehensive wealth database and the influence of wealthy individuals in government as key obstacles. Christoph Trautvetter noted that in Germany, even a small real property tax consumes considerable administrative effort, while a billionaire tax could raise twice as much revenue with just 2,000 declarations, illustrating the potential for efficiency gains. When Florian Schatz from the ATI Secretariat questioned whether a global billionaire tax is suitable for all countries, Christoph Trautvetter emphasised that it’s not just for nations with many billionaires; rather, it depends on how taxes are charged, the level of inequality, and the political will to act. Jocet Dita concluded by noting that in the Philippines, the current focus is on enhancing tax administration to better identify and reach the wealthiest individuals.
