Income Taxes	6 Months Ended
Jun. 30, 2017
Income Taxes
Income Taxes	Note 6—Income Taxes Tax provision and rate—Transocean Ltd., a holding company and Swiss resident, is exempt from cantonal and communal income tax in Switzerland, but is subject to Swiss federal income tax. Our provision for income taxes is based on the tax laws and rates applicable in the jurisdictions in which we operate and earn income. In the six months ended June 30, 2017 and 2016, our estimated effective tax rate, excluding discrete items, was 78.0 percent and 25.7 percent, respectively, based on estimated annual income from continuing operations before income taxes. Our effective tax rate increased in the six months ended June 30, 2017, compared to the six months ended June 30, 2016, primarily due to (a) changes in the relative blend of income from operations in certain jurisdictions and (b) valuation allowances on deferred tax assets for losses not expected to be realized. We consider the tax effect, if any, of the excluded items as well as settlements of prior year tax estimates to be discrete period tax expenses or benefits. In the six months ended June 30, 2017 and 2016, the effect of the various discrete period tax items was a net tax benefit of $147 million and net tax expense of $8 million, respectively. In the six months ended June 30, 2017, such discrete items were primarily related to tax benefit of changes in unrecognized tax benefit associated with tax positions taken in prior years, valuation allowances on deferred tax assets for foreign tax credits not expected to be realized, release of a valuation allowance on deferred tax assets for losses expected to be realized and deductions related to resolution of certain litigation matters related to Macondo well incident. In the six months ended June 30, 2016, such discrete items were primarily related to tax benefit of changes in unrecognized tax benefit associated with tax positions taken in prior years and valuation allowances on deferred tax assets for losses not expected to be realized. For the six months ended June 30, 2017 and 2016, these discrete tax items, coupled with the excluded income and expense items noted above, resulted in an effective tax rate of 4.7 percent and 26.1 percent, respectively, based on income from continuing operations before income tax expense. Tax returns—We file federal and local tax returns in several jurisdictions throughout the world. With few exceptions, we are no longer subject to examinations of our U.S. and non‑U.S. tax matters for years prior to 2010. Our tax returns in the major jurisdictions in which we operate, other than Norway and Brazil, which are mentioned below, are generally subject to examination for periods ranging from three to six years. We have agreed to extensions beyond the statute of limitations in two major jurisdictions for up to 20 years. Tax authorities in certain jurisdictions are examining our tax returns and in some cases have issued assessments. We are defending our tax positions in those jurisdictions. While we cannot predict or provide assurance as to the timing or the outcome of these proceedings, we do not expect the ultimate liability to have a material adverse effect on our condensed consolidated statement of financial position or results of operations, although it may have a material adverse effect on our condensed consolidated statement of cash flows. Norway tax investigations and trial—Norwegian civil tax authorities have challenged certain transactions undertaken by our subsidiaries in 1999, 2001 and 2002. On June 26, 2014, the Norwegian district court in Oslo ruled that our subsidiary was liable for the civil tax assessment but waived all penalties and penalty interest. On January 9, 2017, the Norwegian appeal court in Oslo ruled entirely in favor of our subsidiaries and overturned the district court with respect to the remaining question of principal tax obligations. On February 10, 2017, the tax authorities filed an appeal with the Norwegian Supreme Court. On June 16, 2017, the Norwegian Supreme Court rejected the appeal, formally closing the dispute in our favor. At June 30, 2017, we had no remaining outstanding tax assessments in Norway. Brazil tax investigations—In December 2005, the Brazilian tax authorities issued a tax assessment with respect to our tax returns for the years 2000 through 2004, which is currently for an aggregate amount of BRL 839 million, equivalent to approximately $254 million, including penalties and interest. On January 25, 2008, we filed a protest letter with the Brazilian tax authorities for this tax assessment, and we are currently engaged in the appeals process. On May 19, 2014, the Brazilian tax authorities issued a tax assessment with respect to our Brazilian income tax returns for the years 2009 and 2010, which is currently for an aggregate amount of BRL 143 million, equivalent to approximately $43 million, including penalties and interest. On June 18, 2014, we filed a protest letter with the Brazilian tax authorities for this tax assessment. We believe our returns are materially correct as filed, and we are vigorously contesting these assessments. An unfavorable outcome on these proposed assessments could result in a material adverse effect on our condensed consolidated statement of financial position, results of operations or cash flows. Other tax matters—We conduct operations through our various subsidiaries in a number of countries throughout the world. Each country has its own tax regimes with varying nominal rates, deductions, employee contribution requirements and tax attributes. From time to time, we may identify changes to previously evaluated tax positions that could result in adjustments to our recorded assets and liabilities. Although we are unable to predict the outcome of these changes, we do not expect the effect, if any, resulting from these adjustments to have a material adverse effect on our condensed consolidated statement of financial position, results of operations or cash flows.

Note 6—Income Taxes

Tax provision and rate—Transocean Ltd., a holding company and Swiss resident, is exempt from cantonal and communal income tax in Switzerland, but is subject to Swiss federal income tax. Our provision for income taxes is based on the tax laws and rates applicable in the jurisdictions in which we operate and earn income. In the six months ended June 30, 2017 and 2016, our estimated effective tax rate, excluding discrete items, was 78.0 percent and 25.7 percent, respectively, based on estimated annual income from continuing operations before income taxes. Our effective tax rate increased in the six months ended June 30, 2017, compared to the six months ended June 30, 2016, primarily due to (a) changes in the relative blend of income from operations in certain jurisdictions and (b) valuation allowances on deferred tax assets for losses not expected to be realized. We consider the tax effect, if any, of the excluded items as well as settlements of prior year tax estimates to be discrete period tax expenses or benefits. In the six months ended June 30, 2017 and 2016, the effect of the various discrete period tax items was a net tax benefit of $147 million and net tax expense of $8 million, respectively. In the six months ended June 30, 2017, such discrete items were primarily related to tax benefit of changes in unrecognized tax benefit associated with tax positions taken in prior years, valuation allowances on deferred tax assets for foreign tax credits not expected to be realized, release of a valuation allowance on deferred tax assets for losses expected to be realized and deductions related to resolution of certain litigation matters related to Macondo well incident. In the six months ended June 30, 2016, such discrete items were primarily related to tax benefit of changes in unrecognized tax benefit associated with tax positions taken in prior years and valuation allowances on deferred tax assets for losses not expected to be realized. For the six months ended June 30, 2017 and 2016, these discrete tax items, coupled with the excluded income and expense items noted above, resulted in an effective tax rate of 4.7 percent and 26.1 percent, respectively, based on income from continuing operations before income tax expense.

Tax returns—We file federal and local tax returns in several jurisdictions throughout the world. With few exceptions, we are no longer subject to examinations of our U.S. and non‑U.S. tax matters for years prior to 2010. Our tax returns in the major jurisdictions in which we operate, other than Norway and Brazil, which are mentioned below, are generally subject to examination for periods ranging from three to six years. We have agreed to extensions beyond the statute of limitations in two major jurisdictions for up to 20 years. Tax authorities in certain jurisdictions are examining our tax returns and in some cases have issued assessments. We are defending our tax positions in those jurisdictions. While we cannot predict or provide assurance as to the timing or the outcome of these proceedings, we do not expect the ultimate liability to have a material adverse effect on our condensed consolidated statement of financial position or results of operations, although it may have a material adverse effect on our condensed consolidated statement of cash flows.

Norway tax investigations and trial—Norwegian civil tax authorities have challenged certain transactions undertaken by our subsidiaries in 1999, 2001 and 2002. On June 26, 2014, the Norwegian district court in Oslo ruled that our subsidiary was liable for the civil tax assessment but waived all penalties and penalty interest. On January 9, 2017, the Norwegian appeal court in Oslo ruled entirely in favor of our subsidiaries and overturned the district court with respect to the remaining question of principal tax obligations. On February 10, 2017, the tax authorities filed an appeal with the Norwegian Supreme Court. On June 16, 2017, the Norwegian Supreme Court rejected the appeal, formally closing the dispute in our favor. At June 30, 2017, we had no remaining outstanding tax assessments in Norway.

Brazil tax investigations—In December 2005, the Brazilian tax authorities issued a tax assessment with respect to our tax returns for the years 2000 through 2004, which is currently for an aggregate amount of BRL 839 million, equivalent to approximately $254 million, including penalties and interest. On January 25, 2008, we filed a protest letter with the Brazilian tax authorities for this tax assessment, and we are currently engaged in the appeals process. On May 19, 2014, the Brazilian tax authorities issued a tax assessment with respect to our Brazilian income tax returns for the years 2009 and 2010, which is currently for an aggregate amount of BRL 143 million, equivalent to approximately $43 million, including penalties and interest. On June 18, 2014, we filed a protest letter with the Brazilian tax authorities for this tax assessment. We believe our returns are materially correct as filed, and we are vigorously contesting these assessments. An unfavorable outcome on these proposed assessments could result in a material adverse effect on our condensed consolidated statement of financial position, results of operations or cash flows.

Other tax matters—We conduct operations through our various subsidiaries in a number of countries throughout the world. Each country has its own tax regimes with varying nominal rates, deductions, employee contribution requirements and tax attributes. From time to time, we may identify changes to previously evaluated tax positions that could result in adjustments to our recorded assets and liabilities. Although we are unable to predict the outcome of these changes, we do not expect the effect, if any, resulting from these adjustments to have a material adverse effect on our condensed consolidated statement of financial position, results of operations or cash flows.