Irish Tax Compliance Calendar 2026: Key Deadlines for Accountants

Irish Tax Compliance Calendar 2026: Key Deadlines for Accountants

The Irish tax compliance year for 2026 turns on a handful of recurring dates: the CT1 corporation tax return due by the 23rd of the ninth month after year end, the Form 11 income tax deadline of 31 October with a ROS extension to 18 November 2026, bi-monthly VAT returns due by the 23rd, monthly PAYE remittances by the 23rd, and the split capital gains tax payment dates of 15 December and 31 January. Missing them triggers surcharges, interest and, in some cases, restriction of reliefs, so the calendar below sets out each regime in turn.

Dates marked as confirmed reflect Revenue announcements as at June 2026; where a specific 2026 date has not been separately announced, the standard recurring deadline pattern is stated.

When is the corporation tax (CT1) deadline in 2026?

The Form CT1 must be filed through ROS by the 23rd day of the ninth month after the end of the accounting period. So:

• 31 December 2025 year end: CT1 due by 23 September 2026.
• 30 June 2026 year end: CT1 due by 23 March 2027.

Late filing brings a surcharge of 5 per cent of the tax liability (capped at €12,695) if filed within two months of the deadline, rising to 10 per cent (capped at €63,485) thereafter, plus restrictions on the use of certain loss reliefs.

Preliminary corporation tax

Preliminary tax follows the company's size:

• Small companies (corporation tax liability of €200,000 or less in the prior period) pay one instalment by the 23rd day of the month before the accounting period ends, based on either 90 per cent of the current year liability or 100 per cent of the prior year.
• Large companies pay in two instalments: the first by the 23rd of the sixth month of the accounting period (45 or 50 per cent), and the second by the 23rd of the month before the period ends, bringing the total to 90 per cent of the expected liability.

iXBRL financial statements

Most companies must submit iXBRL-tagged financial statements with, or shortly after, the CT1. Revenue's administrative practice allows the iXBRL accounts to be filed within three months after the CT1 deadline, but the CT1 itself is only treated as complete once they are submitted, so building iXBRL into the CT1 workflow is the safe approach.

When is the Form 11 income tax deadline in 2026?

For the 2025 tax year:

• 31 October 2026: standard pay and file deadline for the Form 11, payment of the 2025 balance, and 2026 preliminary income tax.
• 18 November 2026: extended deadline, confirmed by Revenue eBrief No. 034/26, for taxpayers who both file the Form 11 and pay the liability through ROS. If either the filing or the payment happens outside ROS, the 31 October date applies.

Preliminary income tax for 2026 must equal at least 90 per cent of the final 2026 liability, 100 per cent of the 2025 liability, or 105 per cent of the 2024 liability where paid by direct debit. The ROS extension also applies to capital acquisitions tax returns and payments for gifts and inheritances with valuation dates in the year to 31 August 2026, where filed and paid through ROS.

Late Form 11 filing attracts a surcharge of 5 per cent of the liability (capped at €12,695) within two months, and 10 per cent (capped at €63,485) after that.

What are the VAT deadlines in 2026?

The standard VAT return cycle is bi-monthly, with the VAT3 return and payment due by the 23rd of the month following the period end when filed and paid through ROS. The 2026 bi-monthly deadlines are 23 March (Jan/Feb), 23 May (Mar/Apr), 23 July (May/Jun), 23 September (Jul/Aug), 23 November (Sep/Oct) and 23 January 2027 (Nov/Dec).

• Reduced frequency: Revenue may authorise four-monthly, six-monthly or annual filing for smaller liabilities; the 23rd-of-the-following-month pattern still applies.
• Annual RTD: the Return of Trading Details is due with the VAT return following the trader's accounting year end. An outstanding RTD can hold up tax clearance and repayments.
• VIES and Intrastat: VIES statements are due by the 23rd of the month following the period; Intrastat returns by the 23rd of the following month where thresholds are exceeded.

What are the PAYE deadlines for employers?

Under PAYE Modernisation, payroll submissions are real-time: details must be reported to Revenue on or before each payday. The monthly statement issued by Revenue becomes the return, and payment of PAYE, PRSI, USC and LPT deducted is due by the 23rd of the following month for employers filing and paying through ROS (the 14th for the small minority outside ROS). Employers on Revenue-approved quarterly or annual remittance arrangements pay by the 23rd after the quarter or year end.

Enhanced Reporting Requirements (ERR) also continue: certain non-taxable payments to employees, such as travel and subsistence and the small benefit exemption, must be reported on or before payment.

When is capital gains tax due in 2026?

CGT has a split payment pattern that catches people out because payment falls long before the return:

• 15 December 2026: CGT on disposals in the initial period, 1 January to 30 November 2026.
• 31 January 2027: CGT on disposals in the later period, 1 to 31 December 2026.

The corresponding return (on the Form 11, Form 12 or Form CG1) is then due by 31 October of the following year, 2027 for 2026 disposals. Paying on time but filing late, or vice versa, each carries consequences: interest runs on late payment even where the return is timely.

What happens if a deadline is missed?

The consequences vary by tax head, and knowing them helps prioritise when a client has multiple deadlines under pressure:

• Surcharges: late CT1 and Form 11 returns attract the 5 per cent / 10 per cent surcharges described above, calculated on the tax liability before credits in most cases, which can dwarf the interest cost.
• Interest: late payment of income tax, corporation tax and CGT generally accrues interest at 0.0219 per cent per day (roughly 8 per cent per annum), and late VAT and PAYE remittances at 0.0274 per cent per day (roughly 10 per cent per annum). Interest runs from the original due date regardless of when the return is eventually filed.
• Loss relief restriction: a late CT1 restricts the use of certain reliefs, including group relief and loss offsets, by 25 or 50 per cent depending on how late the return is, subject to caps. For loss-making groups this is often the most expensive consequence of all.
• Tax clearance: outstanding returns or liabilities block tax clearance certificates, which in turn jeopardises public sector contracts, grants and certain licences.
• Preliminary tax shortfalls: underpaying preliminary tax does not trigger a surcharge but exposes the full liability to interest back to the preliminary tax due date, which is why the 100-per-cent-of-prior-year rule is the safe harbour most practitioners use for volatile incomes.

Practice management tips for the 2026 cycle

• Work back from 18 November: the ROS extension compresses badly when client records arrive in October. Set internal cut-offs for receiving records in late summer and communicate them now.
• Stagger corporation tax work by year end month rather than treating 23 September as the only CT1 event; companies with non-December year ends generate deadlines all year round.
• Diarise the CGT payment dates separately from the filing dates for any client who disposes of assets; the 15 December payment with no accompanying return is the single most commonly missed Irish deadline.
• Check ROS Statements of Account monthly for PAYE clients, since the auto-generated statement becomes the statutory return if not corrected by the 14th of the following month.

Other 2026 dates worth diarising

• 31 March 2026: RZLT (Residential Zoned Land Tax) pattern date for returns and payment, where applicable.
• 31 October / 18 November 2026: CAT pay and file for valuation dates in the year to 31 August 2026 (extension applies to ROS filers).
• Dividend Withholding Tax: returns and payment due by the 14th of the month following the distribution.
• CRO annual returns: not a tax deadline, but the 56-day filing window after the Annual Return Date runs alongside the tax calendar and late filing has knock-on consequences for audit exemption.

A practical tip for practitioners: build the calendar around the recurring patterns, the 23rd for ROS-based remittances, the ninth month for CT1, 31 October core pay and file, and then overlay the annually announced ROS extension once Revenue confirms it each year.

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