we often sell a substantial portion of our products in the last month of each quarter, we may not be able to reduce our inventory purchase commitments in a timely manner in response to customer cancellations or deferrals.



Charges to cost of sales for inventory provisions totaled $59.4 million, $50.1 million and $89.9 million for fiscal years 2015, 2014 and 2013, unfavorably impacting our gross margin by 1.3%, 1.2% and 2.1%, respectively. Sales of inventory that was previously written-off or written-down totaled $32.4 million, $43.4 million and $53.7 million for fiscal years 2015, 2014 and 2013, favorably impacting our gross margin by 0.7%, 1.1% and 1.3%, respectively. As a result, the overall net effect on our gross margin from inventory provisions and sales of items previously written down was an unfavorable impact of 0.6%, 0.1% and 0.8% in fiscal years 2015, 2014 and 2013, respectively.



During fiscal years 2015, 2014 and 2013, the charges we took to cost of sales for inventory provisions were primarily related to the write-off of excess quantities of GPU and Tegra Processor products whose inventory levels were higher than our updated forecasts of future demand for those products. As a fabless semiconductor company, we must make commitments to purchase inventory based on forecasts of future customer demand. In doing so, we must account for our third-party manufacturers' lead times and constraints. We also adjust to other market factors, such as product offerings and pricing actions by our competitors, new product transitions, and macroeconomic conditions - all of which may impact demand for our products.



Please refer to the Gross Profit and Gross Margin discussion below in this Management's Discussion and Analysis for further discussion.



Income Taxes



We recognize federal, state and foreign current tax liabilities or assets based on our estimate of taxes payable or refundable in the current fiscal year by tax jurisdiction. We recognize federal, state and foreign deferred tax assets or liabilities, as appropriate, for our estimate of future tax effects attributable to temporary differences and carryforwards; and we record a valuation allowance to reduce any deferred tax assets by the amount of any tax benefits that, based on available evidence and judgment, are not expected to be realized.

United States income tax has not been provided on a portion of earnings of our non-U.S. subsidiaries to the extent that such earnings are considered to be indefinitely reinvested.



Our calculation of current and deferred tax assets and liabilities is based on certain estimates and judgments and involves dealing with uncertainties in the application of complex tax laws. Our estimates of current and deferred tax assets and liabilities may change based, in part, on added certainty or finality to an anticipated outcome, changes in accounting standards or tax laws in the United States, or foreign jurisdictions where we operate, or changes in other facts or circumstances. In addition, we recognize liabilities for potential United States and foreign income tax contingencies based on our estimate of whether, and the extent to which, additional