in determining our worldwide income tax provision. In the ordinary course of a global business, there are many transactions and calculations where the ultimate tax outcome is uncertain. Some of these uncertainties arise as a consequence of revenue sharing and cost reimbursement arrangements among related entities, the process of identifying items of revenues and expenses that qualify for preferential tax treatment, and segregation of foreign and domestic earnings and expenses to avoid double taxation. Although we believe that our estimates are reasonable, the final tax outcome of these matters could be different from that which is reflected in our historical income tax provisions and accruals. Such differences could have a material effect on our income tax provision and net income in the period in which such determination is made.

Our effective tax rate includes the impact of certain undistributed foreign earnings for which no U.S. taxes have been provided because such earnings are planned to be indefinitely reinvested outside the United States. Remittances of foreign earnings to the U.S. are planned based on projected cash flow, working capital and investment needs of our foreign and domestic operations. Based on these assumptions, we estimate the amount that will be distributed to the U.S. and provide U.S. federal taxes on these amounts. Material changes in our estimates or tax legislation that limits or restricts the amount of undistributed foreign earnings that we consider indefinitely reinvested outside the United States could materially impact our income tax provision and effective tax rate.

We record a valuation allowance to reduce our deferred tax assets to the amount that is more likely than not to be realized. In order for us to realize our deferred tax assets, we must be able to generate sufficient taxable income in those jurisdictions where the deferred tax assets are located. We consider future growth, forecasted earnings, future taxable income, the mix of earnings in the jurisdictions in which we operate, historical earnings, taxable income in prior years, if carryback is permitted under the law, and prudent and feasible tax planning strategies in determining the need for a valuation allowance. In the event we were to determine that we would not be able to realize all or part of our net deferred tax assets in the future, an adjustment to the deferred tax assets valuation allowance would be charged to earnings in the period in which we make such a determination, or goodwill would be adjusted at our final determination of the valuation allowance related to an acquisition within the measurement period. If we later determine that it is more likely than not that the net deferred tax assets would be realized, we would reverse the applicable portion of the previously provided valuation allowance as an adjustment to earnings at such time.

We calculate our current and deferred tax provision based on estimates and assumptions that could differ from the actual results reflected in income tax returns filed during the subsequent year. Adjustments based on filed returns are generally recorded in the period when the tax returns are filed