Taxes Consolidation Act 1997 section 81

Section 81 details the types of expenses that cannot be deducted for tax purposes when calculating business profits under Cases I and II of Schedule D.

• Only deductions specifically permitted by the Tax Acts are allowed when computing taxable trading or professional profits, and a wide range of specified expenses are expressly prohibited.
• Expenses that are not wholly and exclusively for business purposes, personal or domestic expenditure, capital items, and losses unrelated to the trade or profession are all non-deductible.
• Under IFRS, interest and research and development expenditure that is capitalised into the cost of an asset remains tax-deductible, provided no prior deduction or relief has already been given for the same amount.
• For corporation tax purposes, doubtful debts are defined as impairment losses calculated in accordance with generally accepted accounting practice (IFRS 9), and are deductible for accounting periods beginning on or after 1 January 2018.