The Netherlands Retreats From Taxing Unrealized Gains: A Mark-to-Market Administrability Case Study

The Netherlands Retreats From Taxing Unrealized Gains: A Mark-to-Market Administrability Case Study

The Netherlands — a rich country with one of the world's most capable tax administrations — has abandoned, in practice, its attempt to tax unrealized capital gains, and the mechanics of how the bill died are among the strongest new evidence on the administrability question at the center of this topic.

What happened

The "Wet werkelijk rendement" (Actual Return in Box 3 Act), passed by the Dutch House of Representatives in February 2026, would have taxed residents at a flat 36% on the annual increase in value of stocks, bonds, and cryptocurrencies from January 2028 — "whether or not anything was sold." Resistance stalled it in the Senate: senators sent the tax ministry 36 pages of questions, a petition collected more than 61,000 signatures, and coalition senators from the VVD and CDA preferred a levy on realized profits. The Senate debated on June 30 without voting, and on July 7 noted a motion declaring no objection to outright withdrawal. State Secretary Eelco Eerenberg's summer repairs — cutting the rate from 36% to 35%, adding a one-year loss carry-back — "none of it held the line." On Budget Day (September 15, 2026), the 2027 Tax Plan confirmed the pivot: "The Dutch government has abandoned its attempt to tax paper profits... it will instead draft a capital gains tax due only when assets are sold¹," with proposals due spring 2027 and the replacement law unable to reach the statute book before 2029 — possibly 2032, per NOS — at a cost of an estimated €3 billion (~$3.5B) per year in foregone revenue.

Why it matters for wealth-tax administrability

Three empirical lessons stand out:

1. Courts have already rejected notional wealth taxation once. The interim regime exists only because the Dutch Supreme Court's December 2021 "Christmas ruling" struck down the old wealth tax: "the court held that taxing income a person never actually received violates his property rights." The current system still taxes an assumed return — 6.00% on investments in 2026, rising to 6.37% in 2027, against a first €59,357 exemption — but since the 2025 counter-evidence law, "anyone whose real return came in below the assumed figure can declare the actual number and pay on that instead. It cuts one way only." With the 10-year Treasury at 4.94% (macro view, 2026-09-21), a 6.37% assumed return on a broad portfolio is a claim about asset classes most savers don't hold — precisely the valuation-gap problem a wealth tax on unrealized value faces everywhere.

2. No peer uses true mark-to-market. "No European country levies a recurring tax on unrealized capital gains; the closest analogues are one-time exit taxes on departing residents, in force in eight of 27 EU member states, and Denmark's annual mark-to-market treatment of certain fund wrappers." The Netherlands was attempting to become "unique on the continent" and retreated. For US debates (California Prop 40's one-time structure, federal mark-to-market proposals), this is the relevant implementation record: recurring unrealized-gains taxation has never stuck anywhere in Europe.

3. The administration cost is the stated reason, not just ideology. As one practitioner put it, such measures are "very unpopular and more cumbersome and costly to administer for tax authorities" (Paul Correa, Fiduciary Wealth Management). The Dutch retreat was driven by a coalition of Senate resistance, petitions, and administrative burden — a political-economy failure mode, not a valuation-technology failure. That distinction matters: California's Prop 40 is one-time precisely to duck the recurring-valuation problem, but its retroactive residency snapshot creates its own litigation surface (see California Proposition 40 Endgame: Newsom Backs the Ban, Hoover Scores a Net Loss, and the FTB War-Room Problem).

The open question

Whether the climbdown keeps mobile wealth at home is unresolved — warnings that crypto holders would relocate accompanied the February vote, and the four-year wait for a final regime leaves Dutch investors weighing options against "the shrinking club of countries that still tax wealth annually." The spring 2027 proposal (rate, base, transition) is the next datum; a watch is registered for its publication.