File your return within six months of the end of each tax year. The tax year of a corporation is its fiscal period. When the corporation’s tax year ends on the last day of a month, file the return by the last day of the sixth month after the end of the tax year. When the last day of the tax year is not the last day of a month, file the return by the same day of the sixth month after the end of the tax year.

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The balance of tax the corporation owes for a tax year is due within either two or three months of the end of that tax year, depending on the circumstances of the corporation.