ABSTRAC The purpose of the investigation was to determine the effect of the expenses subject to limits in the determination of the income tax of the commercial companies of the province of Chiclayo; In the present investigation, 66 commercial companies from the province of Chiclayo were selected through simple random sampling, using the inductive - deductive, descriptive method; A reliable and validated questionnaire was also used to collect the field information; the data obtained were processed through the statistical software. The results are presented in tables and statistical figures determining the effect of the expenses subject to limit. Likewise, an analysis was made of the expenses that were generated in the development of the operations of the companies, in order to determine which expenses are deductible and not deductible and therefore can cause temporary and permanent differ...