sentences:  Some systems base the timing of recognition on the method of accounting of the taxpayer, possibly with an election by a cash basis taxpayer to recognize the tax at the time properly accrued.Many income tax treaties require that the governments party to the treaty grant FTC even if the domestic law of such party do not grant such credit.Federal systems, such as those in Canada, Switzerland, and the US, may have different rules for allowing a credit for extra-jurisdictional credits at the federal and state levels.