This work compares the tax profit determination regulations applicable in Spain and Germany from a legal perspective. Starting from the constitutional principles of taxation and the types of income, the focus of the study is on examining the profit determination methods of the two comparison countries. For the "estimación directa normal," the Spanish equivalent of the German balance sheet comparison, the respective connections between commercial and tax balance sheets as well as accounting and valuation regulations are analyzed. Additionally, the simplified profit determination methods are also a subject of the work.