Higher Education Accountability Tax Act This bill increases the excise tax on the net investment income of certain private university and college endowments and expands the number of universities and colleges that are subject to the excise tax. Under current law, certain private universities and colleges with 500 or more tuition-paying students (of which more than 50% are located in the United States) and endowment assets of at least $500,000 per student (per student threshold) pay an excise tax in the amount of 1.4% on the net investment income from such endowments. Endowment assets that are used directly in carrying out the institution's tax-exempt educational purpose are excluded from the tax. The bill increases the amount of the excise tax to (1) 10% of the net investment income from a university and college endowment, or (2) 20% of the net investment income from a university and college endowment maintained by an institution that increases tuition over a three-year period (preceding the current tax year) at a rate that is higher than the inflation rate. Under the bill, the tuition price for purposes of determining whether the 20% excise tax rate applies is the average yearly price charged to all first-time, full-time undergraduate students (including students who receive financial aid). Further, the bill expands the number of universities and colleges subject to the excise tax by lowering the per student threshold to $250,000.