It's a paywalled article in Dutch, so I used AI to translate it. The dude is from The Netherlands, but he's mainly referring to the situation in Belgium (interview was in a Belgian magazine). So 'De Wever' refers to the Belgian prime minister, let me know if anything else is unclear, as I didn't check the whooole translation :)

This Dutch tax expert wants to overturn our tax system: “That capital gains tax you have is an excellent idea”

Published: June 10, 2025 · By Peter Casteels

A Dutch tax expert, Reinier Kooiman, wants to completely upend our tax system.

Reinier Kooiman proposes abolishing all taxes and replacing them with a single wealth tax. “Why can’t the government take a small amount from your savings, but it can take 50% from your income?”

Forget the wrangling in the De Wever government about the capital gains tax. During coalition talks, that new tax sparked the toughest debates—but after four months in power, there’s still no compromise.

Compared to total public spending, it’s largely symbolic. In his new book, aptly titled The Strongest Shoulders, Kooiman offers a much more radical, yet well-founded, proposal: eliminate all taxes and replace them with one clear wealth tax. He’ll now try to convince you.

That wasn’t his initial goal. Kooiman—affiliated with the University of Amsterdam and formerly at Deloitte—intended to write an academic history of our tax system. The Strongest Shoulders is partly that. He drew inspiration from medieval Italian city-states.

Kooiman: “My research was purely historical; there was no real history of our taxes. I wanted to trace the principles behind them. Obviously, as a tax expert, I had my own ideas. But only after comparing medieval times to today did I gain new insights.

I had never realized our system redistributes from the poor to the rich. Our taxes vastly increase inequality, while like many, I assumed the opposite. In the Italian city-states, a uniform wealth tax was levied on everyone. Primitive as it sounds, it’s fairer than today’s system.” How it works

Kooiman explains: everyone pays income tax based on ability, but indirect taxes like VAT, excise, and tariffs are flat. Lower-income people spend a larger share of income on consumption, so proportionally pay more taxes.

In countries like the Netherlands and Belgium, income inequality is moderate, but wealth inequality is extreme. Our tax system causes it: wealth is never taxed, while low- and middle-income people struggle to build wealth because they pay too much income tax.

The wealthy can accumulate more easily. Simply raising income tax rates won’t reduce inequality; the super-rich would own an even greater share of wealth overall. Lessons from medieval Italy

Kooiman: “City-states only taxed when major expenses arose—like war. If Genoa needed 4,000 libra, and total wealth was 400,000 libra, everyone paid 1% of their wealth. Tax rates varied yearly, but contributions were equal. They measured ability by wealth, not income.” Modern feasibility

Kooiman admits medieval governments were smaller, less bureaucratic, and more local. Today’s centralized, anonymous systems have moved tax collection far from citizens. Governments now take ~45% of GDP in taxes without public debate over who pays. Why wealth tax fell out of favor

As city-states grew, taxing wealth became complex. Since the 18th century, economists pushed income-based taxation. With capitalism’s rise, capital needed for investment—like railways—shouldn’t be taxed. Kooiman calls this “elitist rhetoric”: if total tax revenue stays the same, there’s still plenty of capital.

No evidence suggests the wealthy manage their money better than those living off income. Practicality

Belgium and the Netherlands already have inheritance taxes, meaning declaring estates isn’t too hard. Income tax on labor might be easy, but capital taxes provoke debate—just look at capital gains tax arguments.

Wealth isn’t volatile, so it’s manageable: if someone reports much less, tax authorities can inspect. The exchange

Freedom and equality guide Kooiman: tax shouldn’t redistribute wealth—redistribution should occur through government spending. People should end up equally rich before and after taxes, achieved by a flat wealth tax. A millionaire pays more in absolute terms but the same percentage—no special targeting.

“A millionaire will pay a lot—but can’t claim they’re being singled out.” Rate needed

Kooiman estimates around 8.5% for the Netherlands; Belgium would be similar. The system is simpler and cheaper. Millions of families currently pay income tax to get social benefits—without income tax, they might not need those benefits. Impact by age

Yes, paying 8.5% of assets annually is steep, especially for homeowners. But young people would pay less and have more chance to buy homes; over-50s would pay more. He estimates young people would benefit and older people would see slight drawbacks.

“On average, people under fifty would pay less; after fifty, a bit more.”

He argues that many older people leave large inheritances—money that sits idle. Meanwhile, younger generations bear heavy income tax burdens. Asset scrutiny concerns

Critics say wealth taxes mean inspecting paintings or wine cellars. Kooiman says no exemptions: otherwise, people hide value. But he believes it’s manageable until inconsistencies arise—then the tax office can investigate. Resistance

“The opposition is immense: it feels like theft.”

Kooiman responds: “Why take 50% from income but not from savings? In my system, no one can say money is taxed twice [income vs. wealth]. We all believe in rewarding work—but in practice, inheritance or lucky sales reward people most. We disadvantage hard workers.” Capital flight

Could wealthy flee or hide assets? He says there are two flight types: moving abroad—which is exaggerated as many resist that—and moving capital via corporations. International tax avoidance is tighter, but tax cuts reduce capital flight fears. Countries used to have 70% top rates; now harder to avoid, maybe rates can rise.

“Capital flight concerns are overblown. Many people won't emigrate just for taxes.” His background

He left Deloitte for law firm Stibbe, and teaches at the University of Amsterdam. He notes fiscal firms both help clients avoid taxes and shape tougher laws. They are not a “trick box”—the system doesn't work like that.

He supports Belgium’s capital gains tax. Simplification plea

Tax reforms are politically sensitive. Belgium keeps adding complexity instead of simplifying. A standalone wealth tax would be a step, but only if paired by eliminating other taxes. Otherwise, people won’t embrace it.

Book: De sterkste schouders, Atlas Contact, 352 pp, €24.99 Bio: Born 1990 in Deventer; tax law at Univ. of Amsterdam; PhD in 2016 on inheritance tax; Deloitte 2009–2025; joining Stibbe; lecturer at UvA.