Income taxes



	For the three months ended June 30				For the six months ended June 30
(in millions of Canadian dollars)	2017		2016		2017		2016
Current income tax expense	$	114	$	27	$	195	$	104
Deferred income tax expense	24		90		91		183
Income tax expense	$	138	$	117	$	286	$	287

During the three months ended June 30, 2017, legislation was enacted to decrease the Saskatchewan provincial corporate income tax rate. As a result of this change, the Company recorded an income tax recovery of $17 million in the quarter related to the revaluation of its deferred income tax balances as at January 1, 2017.

The effective tax rates for the three and six months ended June 30, 2017, were 22.31% and 23.90%, respectively, compared to 26.40% and 24.86%, respectively, for the same periods in 2016.

The estimated 2017 annual effective tax rate for the three months ended June 30, 2017, excluding the foreign exchange gain of $67 million on the Company's U.S. dollar-denominated debt, an insurance recovery of $10 million on legal settlement, the $13 million charge associated with the hedge roll and de-designation, and the $17 million tax recovery described above, is 26.50%.

The estimated 2016 annual effective tax rate for the three months ended June 30, 2016, excluding the foreign exchange gain of $18 million on the Company's U.S. dollar-denominated debt, was 26.93%.

The estimated 2017 annual effective tax rate for the six months ended June 30, 2017, excluding the discrete items of the management transition recovery of $51 million related to the retirement of the Company's Chief Executive Officer, the foreign exchange gain of $95 million on the Company's U.S. dollar-denominated debt, an insurance recovery of $10 million on legal settlement, the $13 million charge associated with the hedge roll and de-designation, and the $17 million tax recovery described above, is 26.50%.

The estimated 2016 annual effective tax rate for the for the six months ended June 30, 2016, excluding the foreign exchange gain of $199 million on the Company's U.S. dollar-denominated debt, was 27.25%.