Tonttiosuuksissa

Tonttiosuuksissa refers to a unique concept in Finnish taxation law. In essence, it is a system of real property taxation where the fundamental tax base is not the value of the property itself, but rather the value of the property's supply.

This system is characterized by separate tax assessments for different parcels of land based on their market value. The taxable value granted to a property is a fixed percentage of its actual market value, as determined by the municipality. The rate at which a taxpayer's property is assessed for taxation purposes is stated to be a fraction ("prosenttiosuhteellinen") of the full market value of the land.

In practice, it means that properties are assessed for taxation based on a locally determined factor, and the final tax amount is then calculated using this assessment. The essence of the system lies in its treatment of each property as a self-contained unit with its own taxable value, despite them being part of larger areas of developed land.

The main effects of tonttiosuuksissa are fixed tax revenues for municipalities, as constant property yields for each municipal unit are taken as a base.