Taxes Consolidation Act 1997 section 70

Case III: basis of assessment

Section 70 sets out how income and profits chargeable under Case III of Schedule D are assessed for income tax purposes, including the single source rule, the treatment of foreign rental losses, and the basis of computation.

• All Case III income is treated as coming from a single source, simplifying the tax assessment by removing the need to apply separate commencement or cessation rules each time a new income source arises or an existing one ceases.
• Foreign rental losses (referred to as "excluded amounts") cannot be set against other Case III income — the single source rule does not allow a deficiency arising on a foreign rental property to reduce the overall Case III computation.
• Case III income tax is computed on the full amount of income or profits arising in the year of assessment, and no deductions are allowed other than those specifically permitted under section 71.
• Where the remittance basis applies, the tax is computed on the full amount of Case III income actually received in the State during the year of assessment, rather than on the amount arising.