ENThe article seeks to emphasize financial accounting importance to tax law. As the fundamental financial accounting equation presupposes the legal nature of financial accounting (importance of legal relations), financial accounting shall also become a core subject-matter of law science. Despite the contradictory case-law examples, analysis of fundamental financial accounting equation, Generally Accepted Accounting Principles, financial accounting methods reveals that legal regulation of corporate income tax could gradually implicate more financial accounting norms and minimize differences between calculating result in financial accounting and for taxation purposes. Keywords: corporate income tax, financial accounting, fundamental financial accounting equation, tax base.