This excerpt taken from the SSRX 20-F filed Jun 27, 2008.
(n) Income taxes
Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. A valuation allowance is provided to reduce the amount of deferred tax assets if it is considered more likely than not that some portion, or all, of the deferred tax assets will not be realized. The effect on deferred tax assets and liabilities of a change in tax rate is recognized in the consolidated statement of income and comprehensive income in the period that includes the enactment date.