Capital gains tax in the Netherlands and Belgium: design, behavior and the need for predictable execution

In the section below, you will find a concise overview of the key tax developments in the Netherlands, Belgium and the wider European context.

The Netherlands: no general tax on realized gains, but box 2 applies to substantial shareholdings

In the Netherlands, most retail investors do not pay tax on realized gains. Their portfolios fall under box 3, which uses a deemed‑return approach. Investors with a substantial interest of at least 5 percent are treated differently. They fall under box 2, where dividends and disposal gains are taxed. From 2026, the rate is 24.5 percent up to 68,843 euros and 31 percent above that amount. This split matters because it shapes how different investment structures are taxed in practice.

Box 3 is moving to actual-return taxation in 2028

Beyond Belgium’s reform, the Netherlands is preparing a structural shift in box 3 from a deemed‑return model to taxation of actual returns. The government’s Wet werkelijk rendement box 3 proposes a hybrid system: in principle an accretion‑based tax on actual returns (income plus unrealized gains/losses), with realization‑based taxation for specific assets such as real estate and shares in start‑ups. The bill provides for a tax‑free results threshold and loss carry forwards above a small annual floor. It was submitted to Parliament on May 19, 2025; following the 2024 delay, the target start date is January 1, 2028, with transitional years continuing the current deemed‑return regime (including the “actual return” rebuttal option). Operationally, this shift is material for data quality, year‑end valuations and loss tracking, and it will require clean interfaces between banks/brokers and the tax administration.

Belgium: from exemption to a 10% tax on realized gains, with layered complexity due to Reynders

Through 2025, private investors in Belgium generally paid no tax on realized gains under normal portfolio management. From January 1, 2026, Belgium plans to introduce a 10 percent tax on realized gains on financial assets, including crypto. This new tax operates next to the existing Reynders tax. Running two regimes in parallel adds complexity. The Reynders tax takes priority, and the Reynders base is deducted from the capital gains base to prevent double taxation. Funds invested entirely in bonds and already in scope for Reynders are exempt from the new capital gains tax.

Belgium also introduces a step‑up at the December 31, 2025 valuation, an opt‑out for self‑filing and an additional six months for banks to implement automated withholding. Retroactive collection from January 1, 2026 remains possible.

Early behavioral impact: investors shift from individual stocks to funds

New reporting from seven major banks shows that Belgium’s planned capital gains tax is already changing investor behavior. ING reports a visible shift from individual stocks to funds. KBC observes the same pattern, although more cautiously. Deutsche Bank notes that some clients switched from stocks to funds at the end of last year. Belfius confirms that instruments with fewer administrative and filing obligations attract more interest. The key reason is simplicity. Investors want to avoid extra reporting steps and frequent realization events.

This early shift is consistent with the logic of the regime. A fund structure allows gains to be reinvested by the fund manager without triggering immediate taxation for the investor. The tax only applies when the fund itself is sold. Investors who manage individual stocks are more likely to realize gains repeatedly and face recurring withholding or filing obligations. In Belgium’s new system, simplicity becomes a driver of portfolio design, even before the tax is formally enacted.

The core principles: neutrality, simplicity and transparency

Neutrality requires equal treatment of equal outcomes. The Dutch system is internally consistent, with clear separation between box 3 and box 2. Belgium reduces the risk of double taxation by giving Reynders priority, although operating two regimes side by side still increases administrative complexity.

Simplicity argues for a single, clearly defined base with predictable calculations. The Belgian experience shows that investors respond quickly to operational frictions. The shift from individual stocks to funds confirms that administrative load influences behavior.

Transparency requires an auditable and continuous record of tax bases, allowances and interactions, especially when retroactive collection may apply. Without clear tracking, cross‑year adjustments become difficult and unexpected outcomes multiply.

The wider European context

France is reconsidering exemptions on primary residences and tightening rules for non‑residents; Italy’s Budget Law 2026 resets thresholds for dividend relief and the participation exemption (PEX) on capital gains; Spain is removing inflation/indexation adjustments, which increases the nominal base; and the UK is raising CGT rates and lowering the annual exemption. Across these changes, the emphasis is on transparency, loss offsetting and operational feasibility. For cross‑border investors, fiscal stability is less of a given, which makes documentation, data quality and timing more important.

Europe's FTT debate: long-running effort, national workarounds

The European Commission’s 2026 Work Programme confirms that the proposal to pursue a Financial Transaction Tax under enhanced cooperation has been withdrawn. Member states continue to implement their own versions instead. France raised its FTT rate to 0.4 percent in 2025. Italy’s 2026 Budget Law adjusts the Italian FTT. Spain continues to operate its national FTT with updated procedures and in‑scope listings published by the tax authority.

For Dutch stakeholders this matters. Any renewed domestic FTT debate will take place in a fragmented landscape. Brokers already reflect this mosaic in their guidance. A coordinated EU solution would reduce frictions and add clarity. Until then, firms need consistent rules per jurisdiction and transparent reporting across regimes.