Taxes Consolidation Act 1997 section 27

Basis of, and periods for, assessment

Section 27 sets out the basis of assessment, and the periods for assessment, of corporation tax.

• A company is assessed to corporation tax on all profits arising in each accounting period, whether or not received in Ireland, less any deductions authorised by the Corporation Tax Acts.
• An accounting period begins when a company first comes within the charge to corporation tax and ends on the earliest of several specified events, including the expiry of 12 months, an accounting date, or a change in trading or residency status.
• Special rules apply when a company is wound up: the existing accounting period ends and a new one begins at the commencement of the winding up, with subsequent periods ending only after 12 months or on completion of the winding up.
• Where the accounting period cannot be determined, the inspector may assess the company for a period of up to 12 months, which stands unless revised or the company demonstrates the true accounting periods on appeal.