Income taxes	9 Months Ended
Sep. 30, 2019
Income taxes
Income taxes	14. Income taxes For the three and nine months ended September 30, 2019, we recorded income tax expense of approximately $19.7 million and $24.9 million, respectively. For the three and nine months ended September 30, 2018, we recorded income tax expense of approximately $1.8 million and $4.2 million, respectively. The increased tax expense for the three and nine months ended September 30, 2019 is primarily the result of estimating U.S. tax liabilities that are not fully sheltered by net operating losses or research and development tax credit carryforwards. This is partially offset by higher discrete tax benefits associated with stock-based compensation. As of September 30, 2019, a full valuation allowance continues to be recorded against our U.S. and Swiss net deferred tax assets. This position is based on an analysis of positive and negative evidence, including analyzing three-year cumulative pre-tax income or loss, projections of future taxable income as well as other quantitative and qualitative information. We may release all or a portion of the valuation allowance in the near-term; however the exact timing and amount of such release continues to be based on our assessment of the factors mentioned above. In the period of a release of the valuation allowance, we would recognize a non-cash increase to net income and a corresponding deferred tax asset on our consolidated balance sheet. Following the release, we would continue to utilize research and development tax credits to offset our tax liabilities, but would begin recognizing a significant provision for income taxes. The majority of this provision would be a non-cash expense until our research and development tax credit carryforwards are fully utilized. The balance of our unrecognized tax benefits (including penalties and interest) increased by approximately $1.8 million during the nine months ended September 30, 2019, of which only $0.1 million was recorded as an increase to noncurrent other liabilities on the condensed consolidated balance sheet. The increase is primarily driven by unrecognized tax benefits related to current year operations and research and development tax credits.

Income taxes

9 Months Ended

Sep. 30, 2019

14. Income taxes

For the three and nine months ended September 30, 2019, we recorded income tax expense of approximately $19.7 million and $24.9 million, respectively. For the three and nine months ended September 30, 2018, we recorded income tax expense of approximately $1.8 million and $4.2 million, respectively. The increased tax expense for the three and nine months ended September 30, 2019 is primarily the result of estimating U.S. tax liabilities that are not fully sheltered by net operating losses or research and development tax credit carryforwards. This is partially offset by higher discrete tax benefits associated with stock-based compensation.

As of September 30, 2019, a full valuation allowance continues to be recorded against our U.S. and Swiss net deferred tax assets. This position is based on an analysis of positive and negative evidence, including analyzing three-year cumulative pre-tax income or loss, projections of future taxable income as well as other quantitative and qualitative information. We may release all or a portion of the valuation allowance in the near-term; however the exact timing and amount of such release continues to be based on our assessment of the factors mentioned above. In the period of a release

of the valuation allowance, we would recognize a non-cash increase to net income and a corresponding deferred tax asset on our consolidated balance sheet. Following the release, we would continue to utilize research and development tax credits to offset our tax liabilities, but would begin recognizing a significant provision for income taxes. The majority of this provision would be a non-cash expense until our research and development tax credit carryforwards are fully utilized.

The balance of our unrecognized tax benefits (including penalties and interest) increased by approximately $1.8 million during the nine months ended September 30, 2019, of which only $0.1 million was recorded as an increase to noncurrent other liabilities on the condensed consolidated balance sheet. The increase is primarily driven by unrecognized tax benefits related to current year operations and research and development tax credits.