Some body parts and organs are hard to be taxed and sometimes that would not make business sense for the State treasury. The attached comic shows what it is about. However, it a local tax were to be imposed on the thoughts generated by accountants, no doubt many a local budget would have gained quite much and no photo radars would be necessary to collect funds. The largest fees would no doubt be generated by the most difficult accounting areas. For instance, the calculation of monthly advanced for CIT and the related thoughts cover several dozen hours a year! (unless you use modern tools that save your time).