Income Tax
Preliminary Income Tax — October Payment
How to calculate and pay your preliminary tax correctly
📅 Key Dates
📋 Overview
Preliminary tax is a payment on account of your current year income tax liability. It is due by 31 October each year and must be paid at the same time as your Form 11 filing. Getting this right avoids an expensive interest charge.
✅ How to File — Step by Step
- Calculate 90% of your expected current year tax liability, OR
- Calculate 100% of your prior year tax liability (safe harbour — no interest applies).
- Pay via ROS as part of your Form 11 submission.
- Include income tax, USC, and PRSI (Class S) in your estimate.
- Use the Preliminary Tax Calculator to estimate the correct amount.
⚠️ Penalty if Missed
If your preliminary tax payment is below 90% of your final liability for the year, interest is charged at 0.0219% per day on the shortfall from 31 October. To avoid this entirely, pay 100% of last year's liability (prior year basis).
📄 Revenue Forms
❓ Frequently Asked Questions
Yes. Paying 100% of the prior year's liability is a "safe harbour" — no interest applies even if your actual liability is higher. This is the most common approach.
You can pay based on 90% of your estimated current year liability. Use the Preliminary Tax Calculator to estimate this, and keep records to justify your calculation if Revenue queries it.
Yes — from your first year. In year one you estimate your liability. Revenue cannot penalise you for an incorrect estimate in year one as long as you pay something.