Box 3 (Netherlands)

Box 3 is the category in the Dutch income tax system for "income from savings and investments" (inkomen uit sparen en beleggen). Unlike most countries, the Netherlands does not tax actual capital gains in Box 3. Instead, the government assumes a fictional (forfaitair) return on your net assets and taxes that assumed amount at 36% (2025 rate).

How it works for prediction market traders

Under Box 3, your prediction market positions count toward your total net assets on January 1. The actual profit or loss you made during the year is irrelevant — only the value of your holdings matters for the deemed return calculation.

Deemed return rates (2025)

The deemed return rate depends on the composition of your assets:

• Savings: Based on actual average interest rates
• Investments (including prediction market positions): Fixed percentage (historically 5.5–6.04%)
• Debts: Offset against assets

The ongoing Box 3 debate

Following the landmark December 2021 Supreme Court ruling (Kerstarrest), the Dutch government is working on replacing the deemed return system with taxation of actual returns, potentially starting in 2027. Until then, a temporary bridging arrangement applies.

Comparison with other countries

The Dutch Box 3 system is unique globally. Most countries tax actual gains — Germany at 25% (Abgeltungsteuer), the US at marginal rates or via capital gains treatment. The Netherlands taxes hypothetical gains, which creates unusual situations: you pay tax even in a losing year, but you might pay less than actual gains would warrant in a profitable year. Only a few other jurisdictions (Belgium's TOB, Norway's exit tax) have anything conceptually similar.

Frequently asked questions

Do I pay Dutch tax on my actual prediction market profits?

No — under the current Box 3 system, you pay tax on a deemed (fictional) return based on the value of your assets on January 1. Your actual trading results are irrelevant for Box 3 purposes.

What if I hold both EUR and USD in my prediction market accounts?

All foreign currency holdings are converted to EUR at the exchange rate on January 1 for Box 3 valuation. USDC and other stablecoin balances are valued the same way.

Is Polymarket on-chain activity visible to Dutch tax authorities?

The Belastingdienst (Dutch Tax Administration) has access to CRS/AEOI data and is increasingly monitoring blockchain activity. Dutch residents are legally required to report all foreign assets including crypto-based prediction market positions.