How do I file Irish self-assessment income tax (Form 11) with Revenue?

Self-assessment in Ireland applies to self-employed individuals, company directors, rental income earners, those with non-PAYE income, and others not fully taxed under PAYE. The main return is the Form 11, filed through Revenue Online Service (ROS) at ros.ie.

The preliminary tax deadline is 31 October each year, by which date you must pay at least 90% of your current year's tax liability (or 100% of last year's tax, whichever is less). The Form 11 itself is due by 31 October for paper filers, but online filers through ROS receive an extended deadline — typically mid-November. Filing online is strongly encouraged and required for most self-assessed taxpayers.

The Form 11 covers all income: self-employment profits, rental income, investment income, foreign income, and PAYE income already taxed at source. You claim reliefs, deductions, and credits on the same return. Revenue issues a Notice of Assessment once the return is processed, showing any balance due or refund.

First-time registrants for self-assessment must notify Revenue of their income using Form TR1. Once registered, you receive a Tax Reference Number and can access ROS. It is advisable to register before your first deadline to avoid penalties.