Abstract
The subject of this article is a question whether and within what scope foreign law institutions could be included while determining tax results based on Polish tax regulations. The problem derived because of a type of financing of a foreign subsidiary known only to foreign law, which became the reason to refuse a dominant Polish company recognition of costs of such financing regarding taxes. Within the analysis, the author presents solutions to this issue shaped in international and national tax law, and the problem of legal basis regarding their application in specific states of fact.