The following table presents the provision for income taxes and our effective tax rate for the three and six months ended March 31, 2018 and 2017 (in thousands):

The effective income tax rate on operations is based upon the estimated income for the year, and adjustments, if any, in the applicable quarterly periods for the potential tax consequences, benefits, resolutions of tax audits or other tax contingencies.

Our effective tax rate for the three months ended March 31, 2018 is higher than the statutory tax rate primarily due to a tax provision for state income taxes and an increase in the deferred tax liability related to indefinite lived assets.

Our effective tax rate for the three months ended March 31, 2018 was higher than the statutory rate primarily due to a change in the valuation allowance.

Our effective tax rate for the six months ended March 31, 2018 is lower than the statutory tax rate primarily due to a tax provision for state income taxes and an increase in the deferred tax liability related to indefinite lived assets being offset by a discrete tax benefit recorded for the impact from the US Tax Reform. The tax provision for the six months ended March 31, 2018 includes discrete tax benefit totaling $0.4 million relating to the US Tax Reform that was recorded in the period ending December 31, 2017.

Our effective tax rate for the six months ended March 31, 2017 was higher than the statutory rate primarily due to a change in the valuation allowance.

On December 22, 2017, President Trump signed into law the “Tax Cuts and Jobs Act” ("US Tax Reform"). The US Tax Reform provides for significant changes in the U.S. Internal Revenue Code of 1986, as amended. Certain provisions of the US Tax Reform will become effective during our fiscal year ending September 30, 2018 with all provisions of the US Tax Reform effective as of the beginning of our fiscal year ending September 30, 2019. As the US Tax Reform was enacted after our year end of September 30, 2017, it had no impact on our fiscal 2017 financial results. The US Tax Reform contains provisions with separate effective dates but is generally effective for taxable years beginning after December 31, 2017.

Beginning on January 1, 2018, the US Tax Reform lowers the US corporate income tax rate to 21% from that date and beyond. We estimate that the revaluation of our US deferred tax assets and liabilities to the 21% corporate tax rate will reduce our net deferred tax liability by approximately $0.4 million and is reflected as a tax benefit in our results for the quarter ending December 31, 2017.

Although we believe we have accounted for the parts of the US Tax Reform that will have the most significant impact on our financials, the ultimate impact of the US Tax Reform on our reported results in 2018 may differ from the estimates provided herein, due to, among other things, changes in interpretations and assumptions we have made, guidance that may be issued, and other actions we may take as a result of the US Tax Reform different from that presently contemplated.