Income taxes	9 Months Ended
Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income taxes	Income taxes The Company's tax provision and the resulting effective tax rate for interim periods is determined based upon its estimated annual effective tax rate, adjusted for the effect of discrete items arising in that quarter. The impact of such inclusions could result in a higher or lower effective tax rate during a particular quarter, based upon the mix and timing of actual earnings or losses versus annual projections. In each quarter, the Company updates its estimate of the annual effective tax rate, and if the estimated annual tax rate changes, a cumulative adjustment is made in that quarter. The Company had an income tax expense of $0.5 million and $0.2 million for the three months ended June 30, 2018 and July 1, 2017, respectively, and an income tax expense of $1.1 million and an income tax benefit of $1.8 million for the nine months ended June 30, 2018 and July 1, 2017, respectively. In fiscal 2017, the Company amended a tax audit settlement agreement with the Dutch Tax Administration, which, among other things, resulted in a release of previously accrued tax liabilities for Sonos Europe B.V. that was partially offset by the establishment of a valuation allowance based on cumulative losses, resulting in a net tax benefit in the first nine months of fiscal 2017. Tax Act On December 22, 2017, President Trump signed the Tax Cuts and Jobs Act (the "Tax Act") into law, implementing a wide variety of changes to the U.S. tax system. Among other changes at the corporate level, the Tax Act includes (i) a reduction in the U.S. federal corporate income tax rate from 35% to 21%, (ii) further limitations on the deductibility of interest expense and certain executive compensation, (iii) the repeal of the corporate alternative minimum tax, (iv) the imposition of a territorial tax system with a one-time repatriation tax on deemed repatriated earnings of foreign subsidiaries and (v) subjecting certain foreign earnings to U.S. taxation through a base erosion anti-abuse tax (“BEAT”) and a new tax related to global intangible low taxed income (“GILTI”). Additionally, certain foreign derived intangible income (“FDII”) may prospectively be subject to a reduced rate of income tax from the statutorily enacted rate of 21%. Some of these changes, including the BEAT, FDII and GILTI provisions, will not come into effect until the Company’s 2019 fiscal year, but because the decrease in the corporate income tax rate was effective January 1, 2018, the Company has reduced the future tax benefits of the Company’s existing U.S. deferred tax assets. However, since the Company maintains a full valuation allowance against these assets, it did not have a material impact on the Company’s results of operations or financial condition. The Company has not recorded a provision related to the one-time transition tax under Section 965 of the Code as the Company has estimated that its foreign subsidiaries have a consolidated deficit in accumulated and current earnings and profits. The Company’s accounting for the elements of the Tax Act is incomplete. The Company has made reasonable estimates of the effects to the condensed consolidated statements of operations and comprehensive loss and condensed consolidated balance sheets and have preliminarily determined that a provision is not required. The ultimate impact of the Tax Act may differ from the above estimates due to potential future legislative action to address questions that have arisen because of the Tax Act, issuance of additional guidance by the Internal Revenue Service (the "IRS") to provide clarity on certain provisions of the Tax Act and any changes in accounting standards for income taxes or related interpretations in response to the Tax Act. The SEC has issued rules that allow for a measurement period of up to one year after the enactment date of the Tax Act to finalize the recording of the related tax impacts. The Company currently anticipates finalizing and recording any resulting adjustments by the end of its fiscal quarter ending December 29, 2018.

Income taxes

The Company's tax provision and the resulting effective tax rate for interim periods is determined based upon its estimated annual effective tax rate, adjusted for the effect of discrete items arising in that quarter. The impact of such inclusions could result in a higher or lower effective tax rate during a particular quarter, based upon the mix and timing of actual earnings or losses versus annual projections. In each quarter, the Company updates its estimate of the annual effective tax rate, and if the estimated annual tax rate changes, a cumulative adjustment is made in that quarter. The Company had an income tax expense of $0.5 million and $0.2 million for the three months ended June 30, 2018 and July 1, 2017, respectively, and an income tax expense of $1.1 million and an income tax benefit of $1.8 million for the nine months ended June 30, 2018 and July 1, 2017, respectively. In fiscal 2017, the Company amended a tax audit settlement agreement with the Dutch Tax Administration, which, among other things, resulted in a release of previously accrued tax liabilities for Sonos Europe B.V. that was partially offset by the establishment of a valuation allowance based on cumulative losses, resulting in a net tax benefit in the first nine months of fiscal 2017.

Tax Act

On December 22, 2017, President Trump signed the Tax Cuts and Jobs Act (the "Tax Act") into law, implementing a wide variety of changes to the U.S. tax system. Among other changes at the corporate level, the Tax Act includes (i) a reduction in the U.S. federal corporate income tax rate from 35% to 21%, (ii) further limitations on the deductibility of interest expense and certain executive compensation, (iii) the repeal of the corporate alternative minimum tax, (iv) the imposition of a territorial tax system with a one-time repatriation tax on deemed repatriated earnings of foreign subsidiaries and (v) subjecting certain foreign earnings to U.S. taxation through a base erosion anti-abuse tax (“BEAT”) and a new tax related to global intangible low taxed income (“GILTI”). Additionally, certain foreign derived intangible income (“FDII”) may prospectively be subject to a reduced rate of income tax from the statutorily enacted rate of 21%. Some of these changes, including the BEAT, FDII and GILTI provisions, will not come into effect until the Company’s 2019 fiscal year, but because the decrease in the corporate income tax rate was effective January 1, 2018, the Company has reduced the future tax benefits of the Company’s existing U.S. deferred tax assets. However, since the Company maintains a full valuation allowance against these assets, it did not have a material impact on the Company’s results of operations or financial condition. The Company has not recorded a provision related to the one-time transition tax under Section 965 of the Code as the Company has estimated that its foreign subsidiaries have a consolidated deficit in accumulated and current earnings and profits.

The Company’s accounting for the elements of the Tax Act is incomplete. The Company has made reasonable estimates of the effects to the condensed consolidated statements of operations and comprehensive loss and condensed consolidated balance sheets and have preliminarily determined that a provision is not required. The ultimate impact of the Tax Act may differ from the above estimates due to potential future legislative action to address questions that have arisen because of the Tax Act, issuance of additional guidance by the Internal Revenue Service (the "IRS") to provide clarity on certain provisions of the Tax Act and any changes in accounting standards for income taxes or related interpretations in response to the Tax Act. The SEC has issued rules that allow for a measurement period of up to one year after the enactment date of the Tax Act to finalize the recording of the related tax impacts. The Company currently anticipates finalizing and recording any resulting adjustments by the end of its fiscal quarter ending December 29, 2018.