Calculate your Corporation Tax liability, preliminary tax options, and key CT filing deadlines. Updated for Budget 2026.
Ireland operates a 12.5% Corporation Tax rate on trading income for limited companies. This applies to profits from the company’s core business activity. Non-trading income (rental income, investment income, certain foreign income) is taxed at 25%. Capital gains made by companies are subject to Capital Gains Tax at 33%.
Companies must pay preliminary Corporation Tax before the end of the accounting period. The amount must be the lower of 90% of the current year’s CT liability or 105% of the prior year’s CT liability (for companies with prior year liability under €200,000). Failure to pay the correct preliminary tax results in a 10% surcharge on the unpaid amount.
Capital allowances allow the cost of capital assets to be deducted against taxable profits over time. Plant and machinery (including computer equipment and most business equipment) is written down at 12.5% per year over 8 years. Motor vehicles are also written down at 12.5% per year, subject to emissions-based restrictions on qualifying cost.
The R&D Tax Credit provides a 25% credit on qualifying research and development expenditure, deducted from the Corporation Tax liability. The credit applies to incremental R&D spend above the base period. Unused credits can be carried forward or in some cases refunded to SMEs.
Preliminary CT is due in the month that is 6 months before the end of your accounting period, on the 21st of that month. For a company with a December year-end, preliminary tax is due on or before June 21st. Payment must be made via Revenue Online Service (ROS).
The CT1 Corporation Tax Return must be filed 9 months after the end of the accounting period, on the 21st of that month. For a December year-end, this is September 21st. The final CT liability (less the preliminary tax already paid) is due with the return. Financial statements (accounts) must be filed with the CRO at the same time.
A company qualifies as “small” for preliminary tax purposes if its previous year’s CT liability was €200,000 or less. Small companies may use the 100% of prior year option (instead of 90% of current year) as an alternative. This can be advantageous in growing businesses where current year profits will be significantly higher than prior year.