This excerpt taken from the AAPL 10-K filed Oct 27, 2009.
Changes in the Companys tax rates, the adoption of new U.S. tax legislation or exposure to additional tax liabilities could affect its future results.
The Company is subject to taxes in the United States and numerous foreign jurisdictions. The Companys future effective tax rates could be affected by changes in the mix of earnings in countries with differing statutory tax rates, changes in the valuation of deferred tax assets and liabilities, or changes in tax laws or their interpretation. In addition, the current administration and Congress have recently announced proposals for new U.S. tax legislation that, if adopted, could adversely affect the Companys tax rate. Any of these changes could have a material adverse affect on the Companys profitability. The Company is also subject to the continual examination of its income tax returns by the Internal Revenue Service and other tax authorities. The Company regularly assesses the likelihood of adverse outcomes resulting from these examinations to determine the adequacy of its provision for taxes. There can be no assurance that the outcomes from these examinations will not materially adversely affect the Companys financial condition and operating results.