Preliminary Tax Calculator Ireland

Preliminary tax is an advance payment of your expected tax liability for the current year, paid by 31 October (or mid-November via ROS). It covers income tax, USC, and PRSI. Self-employed individuals, sole traders, landlords, and anyone with untaxed income must pay preliminary tax. The amount must be at least 90% of your final current-year liability, or 100% of last year's liability, or 105% of last year's liability if paying by direct debit. Missing the deadline or underpaying results in Revenue interest charges.

There are three Revenue-approved methods: (1) 90% Rule — pay at least 90% of your expected current-year total tax liability; (2) 100% Prior Year Rule — pay the full amount you paid the previous year; (3) 105% Prior Year Rule — pay 105% of last year's liability, available only via direct debit. Most self-employed people use the 100% prior year rule for predictability, but if their income has grown significantly, the 90% current year rule may result in a lower preliminary tax payment.

If your preliminary tax payment falls below the required threshold (90% of final liability, or 100%/105% of prior year), Revenue charges interest on the shortfall from 1 November at approximately 8% per year. This is not a fixed penalty — it is a daily interest charge that accumulates until you pay the balance with your Form 11 filing. The interest is in addition to the tax owed and cannot be reduced or waived in most cases.

Preliminary tax for the 2025 tax year is due by 31 October 2025. If you file and pay through Revenue Online Service (ROS), the deadline extends to mid-November 2025. For 2026, the same pattern applies — 31 October 2026 or mid-November via ROS. Missing this deadline triggers immediate interest charges. It is not possible to extend the deadline by paying in instalments unless you use the direct debit option.

Yes. Preliminary tax is not just income tax — it includes income tax, Universal Social Charge (USC), and Pay Related Social Insurance (PRSI) Class S for self-employed people. Many self-employed individuals underestimate their preliminary tax because they only calculate income tax and forget USC and PRSI, which can add several thousand euros to the total bill. This is one of the most common reasons for underpayment penalties.

It is not legally required, but it is strongly advisable. Preliminary tax is part of the broader Form 11 self-assessment process. Getting the calculation wrong — either by underpaying or overpaying — has real financial consequences. An accountant ensures you pay the correct amount, claim all available reliefs (expenses, pension contributions, tax credits), and file Form 11 on time. Our Form 11 service costs €350 and covers the full tax year including preliminary tax planning.