What Is a WOZ Value and Why Does It Matter?

Every property in the Netherlands receives an annual valuation from its municipality. This is the WOZ-waarde (Waardering Onroerende Zaken), and it affects more financial decisions than most property owners realize.

What WOZ is

WOZ is the standardized property valuation system used by all 342 Dutch municipalities. Each municipality assesses every property within its borders once per year, estimating its market value as of January 1 of the preceding year. This reference date is called the peildatum. So the WOZ value you receive in 2025 reflects what your property was worth on January 1, 2024.

The valuations are produced using a combination of comparable sales analysis, property attributes (surface area, construction year, location, maintenance condition), and statistical models. Municipalities must follow the Waarderingskamer's quality standards and are subject to regular audits.

What WOZ is used for

The WOZ value is not just a number on paper. It directly determines several tax obligations and financial calculations:

• OZB (onroerendezaakbelasting): the municipal property tax. Rates vary by municipality, typically between 0.02% and 0.30% of WOZ value annually.
• Waterschapsbelasting: the water authority levy, partially based on WOZ value.
• Eigenwoningforfait: for income tax purposes, homeowners must declare a percentage of their WOZ value as deemed rental income. For 2024, this is 0.35% for properties valued between €75,000 and €1,310,000.
• Mortgage lending: banks and mortgage advisors use WOZ as one reference point when assessing property value, alongside their own appraisals.
• Erfbelasting and schenkbelasting: inheritance and gift tax calculations reference WOZ values.

The lag problem

The structural weakness of WOZ is its lag. Because the peildatum is always January 1 of the year before, a WOZ value is already 12 months old by the time it is issued, and up to 24 months old by the end of its validity period.

In a stable market, this lag is manageable. In the Dutch market of the past five years, it has been significant. The average WOZ increase in 2024 was 4.9% nationally. But this reflected market conditions as of January 1, 2023. In fast-moving local markets, the gap between WOZ and actual market value can be even larger.

For anyone building valuation tools, relying on WOZ alone gives you a picture that is at minimum one year out of date. Combining WOZ with current listing prices and recent transaction data from Kadaster produces a much more accurate estimate.

WOZ-Waardeloket: public access since 2016

Since October 2016, WOZ values for all Dutch properties have been publicly accessible through the WOZ-Waardeloket (wozwaardeloket.nl). Anyone can look up the current WOZ value for any address. Before 2016, WOZ values were only available to the property owner and tax authorities.

The Waardeloket provides the current year's value and the previous year's value, but not the full history. For historical WOZ data, you need to obtain it directly from municipalities or from data providers who have been collecting it over time.

Objecting to your WOZ value

Property owners can file an objection (bezwaar) to their WOZ valuation within six weeks of receiving the assessment. In practice, roughly 3% to 4% of all WOZ valuations are challenged annually, and a significant portion of objections result in a reduced valuation. Several commercial services exist specifically to help homeowners file WOZ objections on a no-cure-no-pay basis.

WOZ in the Voseno data platform

Voseno's upcoming Property API will include WOZ valuations as part of the comprehensive property record, combined with BAG registration data, energy labels from EP-Online, and transaction history from Kadaster. By combining WOZ with real-time listing data from our Aggregator API, developers will be able to build applications that show both the official tax valuation and the current market reality for any Dutch property.