Updated 17 October 2026 · For preliminary tax for 2026, due with your 2025 return

How to calculate preliminary tax in Ireland (with 2026 examples)

Preliminary tax is an advance payment of this year's income tax, USC and PRSI. You pay it at the same time as last year's return. So by 18 November 2026 (ROS) you're settling 2025 and paying ahead for 2026. Here's how to work out the right amount.

The three rules: 90%, 100% or 105%

To avoid interest, your preliminary tax must be at least the lowest of:

All three are measured on the combined bill: income tax plus USC plus PRSI.

Worked example 1: income is rising

Aoife is a single freelance designer with no other income. Her 2025 profit was €36,000. Using 2025 rates, her final 2025 liability is:

Business is better this year and she expects €45,000 profit for 2026, which is roughly €7,989.69 of tax at 2026 rates. Her options:

• 100% of 2025: €5,311.00
• 90% of 2026: €7,190.73

The lowest is €5,311.00, so that's enough to avoid interest. By 18 November 2026 she pays her 2025 balance plus €5,311.00. The remaining roughly €2,679 of her 2026 bill is due with the 2026 return in late 2027, so she should set it aside now.

Worked example 2: income is falling

Same 2025 figures, but Aoife expects 2026 profit to drop to €30,000, roughly €3,704.07 of tax at 2026 rates.

• 100% of 2025: €5,311.00
• 90% of 2026: €3,333.66

She can pay €3,333.66. The catch is that if 2026 turns out better than she estimated and €3,333.66 is under 90% of the real figure, interest can apply. Only use the 90% route with a careful estimate.

Your first year as a sole trader

This is where most confusion comes from. People ask about it again and again in places like r/irishpersonalfinance. In your first year in self-assessment, your preliminary tax can be nil, because the "100% of last year" option is zero. But:

• When you file that first return the following year, you pay the whole first-year bill,
• and also preliminary tax for year two, typically 100% of year one.

So the second November can need close to two years of tax at once. Setting aside a fixed share of every payment you receive avoids the shock. The right share depends on your income, so estimate it with the calculator.

How to pay preliminary tax

1. Log into ROS and complete your Form 11 for 2025. The self-assessment panel asks for your 2026 preliminary tax.
2. Pay through ROS (debit instruction, card, or a single debit). Pay by the ROS deadline to get the 18 November date.
3. Alternatively, set up a direct debit to spread preliminary tax across the year, which also opens up the 105% option.

Quick checklist

• Find your 2025 final liability. It's the total ROS calculates when you complete the 2025 return.
• Estimate 2026 profit honestly and run it through the 2026 rates.
• Pick the lowest safe option. If unsure, 100% of last year is the "can't go wrong" choice.
• Diary the date: 18 November 2026 on ROS.

FAQ

When is preliminary tax for 2026 due?

Preliminary tax for 2026 is due by 31 October 2026, or 18 November 2026 if you file your 2025 Form 11 and pay through ROS.

How much preliminary tax do I have to pay?

To avoid interest you pay the lowest of three amounts: 90% of your final liability for the current year, 100% of your final liability for the previous year, or 105% of the year before that (the 105% option only applies if you pay by direct debit and that year's liability was not nil).

Do I pay preliminary tax in my first year as a sole trader?

In your first year in self-assessment your preliminary tax can be nil, because your previous year's self-assessment liability was nil. You still pay the full first-year bill when you file the following year, alongside preliminary tax for your second year, so set money aside.

Does preliminary tax include USC and PRSI?

Yes. Preliminary tax covers income tax, USC and PRSI together, so calculate all three when you estimate it.

What happens if I pay too little preliminary tax?

If you pay less than the minimum required by the rules, Revenue can charge interest on the tax due. If you overpay, the excess is set against your final liability or refunded once you file.

General information, not tax advice. Sources: Revenue's preliminary tax guidance and 2025 Pay and File guide. Example figures use the single-person rate band and credits for 2025/2026, Class S PRSI at 4.125% (2025) and 4.2375% (2026), and no other income or reliefs.