Income Tax Benefit (Expense). Income tax benefit (expense) for the periods indicated consisted of the following:

The state of Texas has a Texas margins tax (“TMT”), which is a form of business tax imposed on gross margin. Although TMT is imposed on an entity’s gross profit rather than on its net income, certain aspects of TMT make it like an income tax. Accordingly, TMT is treated as an income tax for financial reporting purposes.

Effective Tax Rate. Our effective tax rate in 2016 and 2015 was as follows:

Deferred Income Taxes. Deferred income tax balances reflect the effects of temporary differences between the carrying amounts of assets and liabilities and their tax basis, as well as from NOL carryforwards. We state those balances at the enacted tax rates we expect will be in effect when taxes are paid. NOL carryforwards and deferred tax assets represent amounts available to reduce future taxable income.

NOL Carryforwards. Under Section 382 of the Internal Revenue Code of 1986, as amended (“IRC Section 382”), a corporation that undergoes an “ownership change” is subject to limitations on its use of pre-change NOL carryforwards to offset future taxable income. Within the meaning of IRC Section 382, an “ownership change” occurs when the aggregate stock ownership of certain stockholders (generally 5% shareholders, applying certain look-through rules) increases by more than 50 percentage points over such stockholders' lowest percentage ownership during the testing period (generally three years). For income tax purposes, we experienced ownership changes in 2005, in connection with a series of private placements, and in 2012, as a result of a reverse acquisition, that limit the use of pre-change NOL carryforwards to offset future taxable income. In general, the annual use limitation equals the aggregate value of common stock at the time of the ownership change multiplied by a specified tax-exempt interest rate. The 2012 ownership change will subject approximately $18.8 million in NOL carryforwards that were generated prior to the ownership change to an annual use limitation of $638,196 per year. Unused portions of the annual use limitation amount may be used in subsequent years. As a result of the annual use limitation, approximately $6.7 million in NOL carryforwards that were generated prior to the 2012 ownership change will expire unused. NOL carryforwards that were generated after the 2012 ownership change are not subject to an annual use limitation under IRC Section 382 and may be used for a period of 20 years in addition to available amounts of NOL carryforwards generated prior to the ownership change.

NOL carryforwards that remained available for future use for the periods indicated were as follow (amounts shown are net of NOLs that will expire unused because of the IRC Section 382 limitation):

Deferred Tax Assets and Liabilities. At December 31, 2016 and 2015, we had $0 and approximately $3.6 million, respectively, of net deferred tax assets available for future use. Significant components of deferred tax assets and liabilities as of the dates indicated were as follow:

Valuation Allowance. As of each reporting date, management considers new evidence, both positive and negative, that could impact management’s view regarding future realization of deferred tax assets. A significant piece of objective negative evidence evaluated was the cumulative loss incurred over the three-year period ended December 31, 2016. Such objective evidence limits the ability to consider other subjective evidence, such as our projections for future growth. Based on this evaluation, we recorded a full valuation allowance against the deferred tax assets as of December 31, 2016.

Current Versus Long-Term. Effective April 1, 2016, we adopted the provisions of the FASB ASC guidance that simplifies the presentation of deferred income taxes by requiring that deferred tax liabilities and assets be classified as noncurrent instead of separated into current and noncurrent. Accordingly, our consolidated balance sheet at December 31, 2015 was changed to reclassify approximately $3.5 million previously reported as deferred tax assets, current portion, net to deferred tax assets, net.

Uncertain Tax Positions. We adopted the provisions of the FASB ASC guidance on accounting for uncertainty in income taxes. The guidance clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statements. The guidance also prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The standard also provides guidance on de-recognition, classification, interest and penalties, accounting in interim periods, disclosure and transition.

As part of this guidance, we record income tax related interest and penalties, if applicable, as a component of the provision for income tax benefit (expense). However, there were no amounts recognized relating to interest and penalties in the consolidated statements of operations for the years ended December 31, 2016 and 2015. Our federal income tax returns are subject to examination by the Internal Revenue Service for tax years ending December 31, 2013, or after and by the state of Texas for tax years ending December 31, 2012, or after. We believe there are no uncertain tax positions for both federal and state income taxes.