Whether you’re a startup filing your first return or a growing SME managing multiple income sources, these changes are crucial for ensuring full compliance. This blog post breaks down the new CT1 changes step-by-step, explains how they affect your filing obligations.
The CT1 form is used to file annual corporation tax returns in Ireland. All companies operating in the country are required to file this form, whether they made a profit or not. In 2024, an updated version of the form was introduced, compatible with both online submission (via ROS) and offline completion (via RPF). These updates reflect the evolving tax landscape, including legislative changes, new credits, and additional reporting requirements.
On August 5, 2025, Irish Revenue released new guidance that clarifies and expands on several areas of the CT1. These updates aim to support accurate and complete filing for the 2024 financial year. Here’s what’s new:
New fields added for:
💡 De Minimis Aid
💡 Outbound Payments Defensive Measures
💡 Group Relief
💡 S299 Leases
These additions help capture financial support, inter-company payments, and leasing activities more precisely.
The panel now includes refinements for revenue and expense classifications.
📌 This ensures better accuracy in trading profit calculations and aligns with updated accounting standards.
Further guidance was released on formatting and validating iXBRL (Inline eXtensible Business Reporting Language) submissions.
✅ Proper iXBRL filing is mandatory for most companies and helps Revenue assess data digitally. Mistakes in tagging can result in delays or penalties.
Now includes clear guidance for Non-Resident Landlord Withholding Tax (NLWT). Companies with Irish rental income and overseas ownership structures must comply with new withholding and reporting rules.
Expanded to include detailed information about the Digital Games Credit (Paragraph 5.3).
🎮 This is vital for gaming studios and digital developers operating in Ireland who qualify for R&D-related credits.
Clarifies the rules for calculating and reporting retained earnings within close companies.
⚠️ Often overlooked, this surcharge can apply when profits are retained rather than distributed. Early planning can mitigate liabilities.
This section has been updated with improved definitions and use cases, assisting companies in recovering overpaid tax.
📥 Proper filing in this section can lead to significant tax refunds, especially if your tax credits or preliminary payments were misaligned.
If you’re preparing to file your 2024 CT1, focus on these critical aspects:
✅ Ensure your iXBRL data is correctly tagged and validated
✅ Double-check rental income reporting if your business owns Irish property
✅ Claim the Digital Games Credit only if your project meets the qualifying development criteria
✅ Track group relief and outbound payments carefully if part of a group structure
✅ Understand your R&D expenditure categories under the revised sections
As trusted Blanchardstown accountants, we’ve supported dozens of startups and SMEs through their first—and often most complex—corporate tax returns.
Here’s our practical advice:
💡 Start early: Waiting until the last minute increases your risk of missing key documentation
💡 Cross-check updates: The August 2025 guidance contains nuances that generic CT1 advice may miss
💡 Use professional tools: Filing through the ROS Return Preparation Facility (RPF) ensures compatibility and ease of submission
💡 Consider expert review: Even if you’re confident in your financials, a second pair of eyes can catch missed opportunities for relief
📞 Book a Free 15-Minute CT1 Consultation.
Let’s review your return before you submit it—and ensure you’re not leaving money on the table.
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