What is the taxable basis for savings & investments (grondslag sparen & beleggen)?

Quick Answer

In the Netherlands, the wealth tax is levied on the income from your taxable basis for savings and investments (grondslag sparen en beleggen). Your taxable basis is the value at 00:00:00 on January 1st of your assets minus your debt and your tax-free capital of €50,000.

To see what contributes to your assets and what contributes to your debts you can go to the website of the Belastingdienst

Example:

Thomas has cash worth €40,000, a second home worth €80,000, crypto assets worth €5,000 and study debt of €10,000. Then Thomas's assets are (€40,000 +€80,000+€5,000) and his debts are worth (€10,000), he has a tax-free capital of €50,000. Thomas's taxable basis is then €125,000 - €10,000 - €50,000 = €65,000