Since 1 February 2016, insurance companies in Poland are subject to a tax on certain financial institutions (Journal of Laws 2019, pos.1836 — consolidated version). From the very beginning, the taxpayers subject to this act struggle with proper interpretation of its provisions. This paper aims to present one of the unclear provisions related to the appropriate allocation of tax allowance to insurance/reinsurance entities subject to taxation from the same capital group and decode its proper meaning based on many decisions delivered by administrative courts. To achieve this goal, the author gathered and analysed decisions delivered by administrative courts concerning the above provisions. The detailed analysis of pertinent regulations and case law leads to the conclusion that the most reasonable approach is to apply appropriate IFRS rules while allocation the tax allowance to taxpayers.