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In our series Where Law Meets (your) Business, we highlight how colleagues put their expertise into practice, whether through research, teaching, support roles or in bridging the gap between law and society. We spoke to Willem about the commercial practice versus academia, about solar panels and parking bays, and about the joy of that lightbulb moment.

“What works on paper doesn’t always make sense in practice”

Willem's career started out at the very place he now teaches: our faculty. After working as a tutor for a year, and later at EY, he became a legal officer at the Supreme Court of the Netherlands. There, he contributed to complex tax cases for two Advocates General and the Court itself. “A wonderful period,” he recalls, “It was a rare opportunity to work with legal minds whose names one normally encounters only in court decisions.”  

He later returned to the advisory world, first briefly at a niche tax firm, and since 2018 at Deloitte. As a senior tax adviser, he focuses on complex corporate tax issues, often within sectors such as oil, gas, and shipping, though he also works with domestic businesses. In his own words: “Honestly, I just find everything interesting.”

Consciously choosing not to let go of teaching, he’s been a part-time academic lecturer at Erasmus School of Law since XNUMX. He wears several hats here: course coordinator and lecturer in both the bachelor’s and master’s in tax law, as well as programme coordinator for the post-master programme ‘International and European Tax Law’ at EFS, Erasmus Fiscal Studies. Willem believes this combination of practice and academia is vital: “You see the rules in action, and you can bring that real-world experience straight into the lecture hall. It keeps the teaching sharp and relevant.”

Parking fees, solar panels, and a living field of law

Willem enjoys making tax law tangible by drawing on everyday examples. “Take parking tax,” he explains. “You’re only allowed to charge tax if someone parks in a designated bay. But what if a car has two wheels on the pavement next to the bay? Are they still technically in the bay? Are you allowed to charge tax or not? These kinds of questions really stick.”

He also brings in larger, more complex cases, such as a solar park that floats on water rather than being fixed to the ground. “Then the question becomes: is this real property? Fiscally, that distinction matters a lot. And the answer depends on the details; is it anchored, are there cables going to shore, can it be easily moved?” He grins. “I enjoy cases where it’s not immediately clear. The rules might look clear on paper, but the moment you apply them, reality gets messy.” For Willem, tax law is anything but dull. “It’s fascinating precisely because the rules are never truly finished. That’s what makes the field alive.”

Taxation in service of shifting norms

He sees this dynamism reflected elsewhere too. “Structures that were commonplace ten years ago are now viewed as undesirable, even unethical,” he says. “Especially in international tax planning, constructions that were legal and accepted back then are now under fire.”

Such shifts raise complex legal questions. “Can you hold people accountable for choices made under a different legal framework, at a different time? And what does that say about public trust in taxation more broadly?”

He pauses. “Tax, at its core, is an expression of solidarity. But it’s also a system of rules, numbers and consequences. So you're constantly having to assess what you believe is fair, and then figure out how to express that legally and fiscally.”

Will he ever don a robe?

Willem isn’t ruling it out. “I’ve thought about it. The role of judge appeals to me, particularly because it’s where you apply laws to real-world situations, often where theory and reality clash.” Still, he hesitates. “It’s a massive responsibility. You’re passing judgment on people, in situations that are rarely black and white. But that tension between law and life, that's what fascinates me.”

For now, he feels perfectly at home, dividing his time between the classroom and the advisory world. “Maybe one day it’ll happen. But right now, I’m happy helping the next generation think about rules, their function, and their limits.”

Grounded in both academia and practice

Willem feels closely connected to Erasmus School of Law. “I’m proud to be part of this faculty. There’s real freedom, space for development, and colleagues with extraordinary expertise.” He does think departments could engage with each other more. “There’s so much knowledge in-house. It would be great if we shared it more actively.”

One of our faculties strengths, in his view, is its connection to practice. “Many colleagues work here part-time. That can raise questions about conflicts of interest, sure, but it also brings something crucial: we feed up-to-date, practical knowledge directly into our teaching. It makes the education stronger and more relevant.”

Where Law Meets (your) Business: “At my best when someone says: ‘Ah, so that’s how it works’”

Willem’s ‘business’ isn’t just about structuring clever solutions or tackling high-end tax cases, though he does those too. “I want students to understand why the rules are the way they are,” he explains. “Not because they need to pass an exam, but because they’re genuinely curious, because they want to understand.” That moment of clarity, that’s the essence of his work. “Not to give all the answers, but to puzzle things out together. To spark curiosity.”

He sees teaching as more than just passing on knowledge. “It’s about helping students see. That moment when someone sits up straight and thinks: ‘This is interesting. Now I get it.’ That’s when the magic happens. That’s what it’s all about.”