Quarterly report pursuant to Section 13 or 15(d)

Income Taxes

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Income Taxes
6 Months Ended
Jun. 30, 2018
Income Tax Disclosure [Abstract]  
Income Taxes
Income Taxes
We file a consolidated federal income tax return for all of our wholly-owned subsidiaries, including Sirius XM.  For the three months ended June 30, 2018 and 2017, income tax expense was $70,570 and $119,513, respectively, and $150,819 and $233,486 for the six months ended June 30, 2018 and 2017, respectively.
Our effective tax rate for the three months ended June 30, 2018 and 2017 was 19.4% and 37.2%, respectively. Our effective tax rate for the six months ended June 30, 2018 and 2017 was 20.6% and 36.3%, respectively. The effective tax rate for the three and six months ended June 30, 2018 was primarily impacted by the reduced federal income tax rate as a result of the Tax Act and the recognition of excess tax benefits related to share based compensation. The effective tax rate for the three and six months ended June 30, 2017 was impacted by the recognition of excess tax benefits related to share based compensation. We estimate our effective tax rate for the year ending December 31, 2018 will be approximately 22%.
As of June 30, 2018 and December 31, 2017, we had a valuation allowance related to deferred tax assets of $52,405 and $52,883, respectively, that were not likely to be realized due to certain net operating loss limitations and acquired net operating losses that were not more likely than not going to be utilized.