	Three Months Ended March 31						Six Months Ended March 31
	2019			2018			2019			2018
	(Dollars in millions)
(Provision) benefit for income taxes	$	(20	)	$	7		$	(13	)	$	(198	)
Effective tax rate		41	%		4	%		11	%		(248	)%

For the three and six months ended March 31, 2019, the tax (provision) benefit included a net discrete tax expense of less than $1 million and a net discrete tax benefit of $24 million, respectively, of which nil and $17 million, respectively, comprised the impact of the Act. For the three and six months ended March 31, 2018, the tax (provision) benefit included a net discrete tax benefit of $26 million and a net discrete tax expense of $162 million, respectively, of which net tax expenses of $4 million and $189 million, respectively, comprised the impact of the Act.

On December 22, 2017, the U.S. enacted significant changes to federal income tax law affecting the Company, including a permanent reduction of the U.S. corporate income tax rate from 35% to 21%, effective January 1, 2018, as well as a 100% dividend received deduction for foreign dividends. Although the passage of the Act reduced the U.S. tax rate and effectively created a participation exemption regime for foreign earnings, certain other aspects of the new legislation, including in particular, immediate U.S. taxation of global intangible low-taxed income (“GILTI”) earned by foreign subsidiaries, will have a negative impact on earnings. In transitioning to this participation exemption regime, Cabot was also subject, during fiscal 2018, to a one-time tax on the deemed repatriation of certain foreign earnings.

As provided in Staff Accounting Bulletin 118 (“SAB 118”), the Company made certain final adjustments during the first quarter of fiscal 2019 related to the U.S. taxation of deemed foreign dividends in the transition fiscal year. For the six months ended March 31, 2019, the Company recorded an additional provisional tax benefit of $17 million related to the U.S. taxation of deemed foreign dividends in the transition fiscal year. This benefit may be reduced or eliminated in future legislation. If such legislation is enacted, Cabot will record the impact of the legislation in the quarter of enactment.

Cabot and certain subsidiaries are under audit in a number of jurisdictions. In addition, certain statutes of limitations are scheduled to expire in the near future. It is reasonably possible that a further change in the unrecognized tax benefits may also occur within the next twelve months related to the settlement of one or more of these audits or the lapse of applicable statutes of limitations. However, an estimated range of the impact on the unrecognized tax benefits cannot be quantified at this time.

Cabot files U.S. federal and state and non-U.S. income tax returns in jurisdictions with varying statutes of limitations. The 2014 through 2017 tax years generally remain subject to examination by the IRS and various tax years from 2005 through 2017 remain subject to examination by the respective state tax authorities. In significant non-U.S. jurisdictions, various tax years from 2002 through 2017 remain subject to examination by their respective tax authorities. As of March 31, 2019, Cabot’s significant non-U.S. jurisdictions include Canada, China, France, Germany, Italy, Japan, and the Netherlands.

During the three and six months ended March 31, 2019, Cabot released uncertain tax positions of $1 million and $8 million, respectively, due to audit settlements and the expiration of statutes of limitations in various jurisdictions. During the three and six months ended March 31, 2018, Cabot released uncertain tax positions of less than $1 million and $2 million, respectively, due to the expirations of statutes of limitations in various jurisdictions.