The article discusses the questions connected with the differences between Polish balance sheet law and tax law. This issue is particularly important while analysing the possibilities of using the so called „pillow tax”. The differences in question are caused by the fact that the balance sheet law treats some of the issues differently than the tax law. However, in both cases the basis for determining the tax results is the records kept by a given company. In this area there are also different definitions of the relationship between the actions resulting from this two, formally equivalent to one another, acts. From the theoretical perspective balance sheet law is of greater importance consisting in the accountancy law as the basis for determining a financial outcome. On the other hand, the tax law seems to be more important in accounting, as by applying unambiguous solutions it limits the number of alternatives propounded by Polish balance sheet law. Due to these differences, new balance categories connected with accounting for the deferred income tax need to be created. The article also presents the similarities and differences between these two laws in other countries.