Higher Education Accountability Tax Act This bill increases from 1.4% to 10% the rate of the excise tax on the net investment income of applicable educational institutions (i.e., certain private colleges and universities). It further increases to 20% the rate of such tax on net-price-increase institutions (i.e., educational institutions whose net price increased at a rate exceeding the rate of increase in the Consumer Price Index during a specified three-year period). The bill also modifies the definition of applicable educational institution to lower the per student threshold in that definition from $500,000 to $250,000 (thus making more such institutions subject to the excise tax).