The text contains basic information on business taxes in context of changes introduced on January 1, 2013 regarding the necessity to correct the costs in situation when the dues were not payed on time or when the date due is longer then the period regulated by law. The changes influence economic activity because they deprive the taxpayer of the right to consider expense as tax deductible in case when during certain period he had not payed the contractor. The reason for the change was increasing liquidity of transactions between enterprises through penalizing overdue payments. However, aside of the tax code the matter is also regulated by the transaction payment regulation act. The dualism of regulation, due to its fiscal effect (the beneficiary of new regulation is the treasury) causes the author to doubt the rationality of the new legislation.