Hjalte Fejerskov Boas

I am a postdoctoral researcher at CEBI (Center for Economic Behaviour and Inequality) and the Department of Economics at the University of Copenhagen.

My research focuses on international taxation and public finance, with a particular interest in how governments can design effective tax systems in an increasingly globalized and digitalized economy.

From 2026 to 2028, I hold an Independent Research Fund Denmark International Postdoctoral Grant for the project Tax Enforcement Across Borders.

Beyond academia, I serve as a short-term expert for the International Monetary Fund (IMF), where I contribute research and analytical expertise to support tax administration reforms and capacity-building efforts in member countries.

CV: Link

Email: hfb@econ.ku.dk

Mobile: (+45) 28 26 41 48

X: https://twitter.com/Hjaltefb, BSky: Bsky.app/hjaltefb,
LinkedIn: https://www.linkedin.com/in/hjaltefejerskovboas/

Google Scholar: Link

Research

Working papers

Taxing Capital in a Globalized World: The Effects of Automatic Information Exchange | with Niels Johannesen, Claus Thustrup Kreiner, Lauge Truels Larsen, and Gabriel Zucman

Reject and resubmit at Journal of Political Economy

NBER Working Paper 2024

Media coverage: Vox EU, Zetland

Abstract: In the second half of the 2010s more than 100 countries—including all large offshore financial centers—started to automatically exchange bank information with foreign tax authorities. This informational big-bang marks a break with the situation of offshore bank secrecy that prevailed before. We study its effects on tax compliance by analyzing the universe of information reports sent by foreign banks to Danish authorities, matched to population- wide micro-data on income, wealth, and cross-border bank transfers. In response to the automatic exchange of bank information, tax evaders may repatriate previously undeclared offshore wealth, they may start to self-report offshore income to the tax authorities, or the tax authorities may detect their evasion in audits that use the new information reports. Using a variety of research designs, we find large compliance effects along all these margins, with the largest response coming from repatriation of wealth. Overall we estimate that the automatic exchange of bank information has closed about 70% of the offshore tax gap. These results highlight the power of international cooperation to improve tax compliance in a globalized world.

Enforcing Taxes on Cryptocurrencies | with Mona Barake

CEBI Working Paper 2024, EU Tax Observatory Working Paper

Awards: Heinz-König 2nd prize. ZEW - Leibniz Centre for European Economic Research

Media coverage: Taxnotes, Cryptonews.com

Abstract: Cryptocurrencies pose substantial challenges to tax enforcement due to their anonymous and decentralized properties, undermining conventional regulatory practices. We study the impact of an ambitious new enforcement initiative aimed at addressing these challenges: domestic third-party reporting of crypto income. We estimate tax compliance and behavioral responses to this new policy by combining unique Danish microdata from domestic crypto platforms, administrative tax records, and cross-border bank transfers. Despite the introduction of domestic third-party reporting, over 90% of crypto investors do not declare crypto income. Moreover, we identify a significant and persistent evasion response to the policy as investors shift trading activity from domestic platforms, subject to third-party reporting, to foreign platforms outside regulatory reach. Our findings underscore the limits of domestic enforcement strategies in addressing tax evasion for decentralized, borderless assets like cryptocurrencies, highlighting the need for international coordination.

Did Automatic Exchange of Information End Bank Secrecy? Evidence from Aggregate Administrative Data | with Matthew Collin, Sarah Godar, Carolina Moura, and Andreas Økland

Skatteforsk working paper

Abstract: This paper evaluates the scope and coverage of the Common Reporting Standard (CRS), an international automatic exchange of information regime intended to eliminate bank secrecy and reduce cross-border tax evasion. We obtain new, aggregated CRS data from 26 countries, covering roughly 30% of the global amount reported by the OECD for the year 2022. We first show that cross-border financial wealth continues to be concentrated in tax havens. We then combine our aggregate CRS data with recent estimates of offshore financial wealth to estimate the coverage of the CRS. Our results suggest a coverage rate ranging from 38 to 93% for the subsample of countries we have the most granular data from, highlighting scope for improvement. However, we also show that the volume of data exchanged internationally has increased and improved in quality substantially over recent years, giving reason for longer-term optimism.

Work in progress

The transparency dividend: Dynamic effects of tax audits on offshore income | with Niels Johannesen, Claus Thustrup Kreiner, Lauge Truels Larsen, and Gabriel Zucman

Preregistration

Abstract: With the vast expansion of cross-border information exchange, tax authorities now receive comprehensive and granular third-party reported data about taxpayers' foreign financial accounts. Nonetheless, non-compliance remains much higher on offshore accounts than on domestic ones. This paper studies the deterrence effects of a policy tool designed to reduce the offshore tax gap: Tax audits that target foreign financial income and lever the new information flows about foreign accounts to select likely non-compliant taxpayers. The results of a randomized control trial implemented by the Danish tax authorities show that the targeted audits have a significant positive impact on tax compliance. For each dollar of non-compliant foreign income uncovered in the audits, self-reporting increases by around 0.1 in the first year after the audit and by almost 0.2 in each of the following three years. While the audits cause more self-reporting of foreign financial income, they do not induce taxpayers to rely less on foreign accounts.

Teaching

Lecturer:

2024: Introduction to Social Data Science (BSc/MSc level)
2022: Introduction to Social Data Science (BSc/MSc level)

Teaching assistant:

2021: Economics in Society (BSc level)