(1) In this section -
"accounting period" includes a part of an accounting period;
"external tax" means a tax chargeable and payable under the law of the territory in which the paying company is resident, being a territory to which this section applies, and which corresponds to Irish corporation tax or income tax or both of those taxes, but a tax payable under the law of a province, state or other part of a country, or which is levied by or on behalf of a municipality or other local body, shall for the purposes of this subsection be deemed not to correspond to those taxes.
(2) This section shall apply to every territory other than a territory with the government of which arrangements are for the time being in force by virtue of section 826(1).
(3) Where a company (in this section referred to as "the investing company") has paid by deduction or otherwise, or is liable to pay, by reference to any part of its income arising in a territory to which this section applies, tax for any account
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