Note 6 — Income Taxes

The effective tax rate was 12.7% and 18.7% for the six months ended November 30, 2016 and 2015, respectively. The decrease in the Company's effective tax rate was primarily due to a discrete benefit related to the resolution of a foreign tax credit matter with the U.S. Internal Revenue Service (IRS). The Company also benefited from a one-time adjustment to a deferred tax asset related to the nonqualified deferred compensation plan.

As of November 30, 2016, total gross unrecognized tax benefits, excluding related interest and penalties, were $397 million, $174 million of which would affect the Company’s effective tax rate if recognized in future periods. As of May 31, 2016, total gross unrecognized tax benefits, excluding related interest and penalties, were $506 million. The liability for payment of interest and penalties increased $11 million during the six months ended November 30, 2016. As of November 30, 2016 and May 31, 2016, accrued interest and penalties related to uncertain tax positions were $220 million and $209 million, respectively (excluding federal benefit).

The Company incurs tax liabilities primarily in the United States, China and the Netherlands, as well as various state and other foreign jurisdictions. The Company is currently under audit by the IRS for fiscal years 2013 through 2016. As previously disclosed, the Company received statutory notices of deficiency for fiscal 2011 and fiscal 2012 proposing a total increase in tax of $254 million, subject to interest, related to a foreign tax credit matter. The Company contested these deficiencies by filing petitions with the U.S. Tax Court. During the three months ended August 31, 2016, the Company reached a resolution with the IRS on this matter. Decisions were subsequently filed in U.S. District Tax Court stating there is no deficiency in income tax due from the Company. The Company has now resolved all U.S. federal income tax matters through fiscal 2012.

The Company’s major foreign jurisdictions, China and the Netherlands, have concluded substantially all income tax matters through calendar 2005 and fiscal 2010, respectively. Although the timing of resolution of audits is not certain, the Company evaluates all domestic and foreign audit issues in the aggregate, along with the expiration of applicable statutes of limitations, and estimates that it is reasonably possible the total gross unrecognized tax benefits could decrease by up to $170 million within the next 12 months.