23rd of the penultimate month before year-end (ROS).
Preliminary Tax (Companies)
Advance Corporation Tax payment due one month before company year-end (specifically the 23rd of that month for ROS users). 90% of current year liability or 100% of prior year for small companies.
Who this applies to
- All Irish-resident companies with a CT liability over €200,000 prior year (otherwise 100% prior year is enough)
- New companies in their first accounting period are exempt
What to file
Preliminary tax payment via ROS — no form required, just the cash payment.
How to file
Pay via ROS using single debit instruction or RDI direct debit.
Payment due
23rd of penultimate month before year-end.
Penalties for missing this deadline
Daily interest at approximately 8% annualised on shortfall from due date until paid. No fixed-amount penalty.
Filing checklist
- Estimate current year CT liability (90% threshold)
- Or use 100% of prior year CT (small company option)
- Pay via ROS by the 23rd
- Keep ROS receipt for CT1 reconciliation
Common mistakes to avoid
- Paying the wrong amount and triggering interest
- Forgetting to pay because there is no return to file
- Using current year estimate when prior year would have sufficed (capital tied up)
Never miss a Ireland deadline
AccountsOS tracks every Revenue (Revenue Commissioners) and Companies Registration Office (CRO) deadline and reminds you weeks ahead.
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