Income Taxes
We are not a taxable entity for U.S. federal income tax purposes or for the majority of states that impose an income tax. Taxes on our net income are generally borne by our partners through the allocation of taxable income. Our income tax provision results from state laws that apply to entities organized as partnerships. For us, this is primarily Texas. Our effective tax rate was less than one percent for the years ended December 31, 2017, 2016 and 2015.
At December 31, 2017 and 2016, we had a deferred tax liability of $5 million and $2 million, respectively. The net deferred tax liability was primarily associated with PP&E and equity investments.
As of December 31, 2017 and 2016, we had no liability reported for uncertain tax positions, and we did not have any interest or penalties related to income taxes for the years ended December 31, 2017, 2016 and 2015. Texas tax returns for the years 2013 and forward are subject to examination.