Questão jurídica principal
Whether a tax authority may first assess according to the prior intercantonal allocation practice and later issue a mid-period supplementary assessment based only on a new legal view, without any factual change.
Decisão extraída
No. If the authority concludes that the existing intercantonal tax allocation is incorrect and wants to change it in its favor, it must do so with the main assessment at the start of the tax period; a later interim assessment is impermissible when only the legal assessment has changed and the facts have remained the same.
Fundamentação extraída
A supplementary assessment for changed allocation is only justified if the relevant circumstances have changed. Here, the authority did not rely on a factual change, but merely on a revised legal assessment. That cannot justify a later interim assessment for the same tax period.