Key Tax Compliance Deadlines

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With a number of important tax compliance deadlines falling between now and early 2027, it is worth taking the time to review upcoming obligations and ensure you are prepared well in advance. Below, we outline some of the key filing and payment deadlines and points to consider before submitting returns.

Capital Acquisitions Tax (CAT)

The valuation date is a critical factor for CAT purposes, as it determines when the CAT return must be filed and when any tax liability becomes payable.

The pay and file deadlines are as follows:

• Valuation dates between 1 January and 31 August: filing and payment are due by 31 October of the same year.
• Valuation dates between 1 September and 31 December: filing and payment are due by 31 October of the following year.

It is important to note that where the IT38 return is filed online and payment is made online, the deadline for gifts or inheritances with valuation dates in the year ending 31 August 2026 is extended to Wednesday, 18 November 2026.

Determining the Valuation Date

Establishing the correct valuation date is essential, as it determines the CAT compliance timeline.

For a gift, the valuation date is generally the date on which the gift is transferred.

For an inheritance, determining the valuation date can be more difficult. In most cases, it is the earliest of:

• The date on which the executor or administrator is entitled to retain the asset for the beneficiary;
• The date on which the asset is actually retained; or
• The date on which the executor or administrator transfers the asset to the beneficiary.

CAT Return Requirements

The requirement to file a CAT return should be considered when a gift or inheritance is received.

A return may be required even where no tax liability arises. For example:

• Where the beneficiary has used more than 80% of the relevant tax-free threshold; or
• Where reliefs such as Agricultural Relief or Business Relief are being claimed.

Capital Gains Tax (CGT)

The payment deadlines for CGT liabilities arising in 2026 are:

• Disposals made between 1 January 2026 and 30 November 2026: CGT is payable by 15 December 2026.
• Disposals made between 1 December 2026 and 31 December 2026: CGT is payable by 31 January 2027.

For companies, tax on chargeable gains generally falls due under the normal corporation tax payment and filing rules. However, where a company disposes of development land and a CGT liability arises, the standard CGT payment deadlines above apply.

Reporting CGT Disposals

The method of reporting a CGT disposal depends on the taxpayer's circumstances.

Individuals who are chargeable for income tax and file a Form 11 should report disposals on their annual income tax return.

In certain cases, particularly where an individual has only PAYE income or non-PAYE income of less than €5,000, a Form 12 (paper or online) may be used. Where neither option is appropriate, a Form CG1 can be filed to report the disposal.

Corporation Tax

Corporation tax filing deadlines depend on a company's accounting period. For companies with a 31 December 2025 year-end, the CT1 return will be due by 23 September 2026.

In addition to annual filing obligations, companies should also ensure they remain compliant with their preliminary tax requirements.

Preliminary Tax Deadlines

For large companies with an accounting period running from 1 January 2026 to 31 December 2026:

• The first preliminary tax instalment was due on 23 June 2026.
• A second instalment will be due on 23 November 2026.

If the June deadline was missed, any outstanding preliminary tax should be paid as soon as possible to minimise potential interest charges.

For small companies with the same accounting period, preliminary tax is payable in a single instalment by 23 November 2026.

Don't Forget the Other Compliance Obligations

While the deadlines above represent some of the most significant tax obligations over the coming months, businesses and individuals should also keep on top of ongoing obligations such as:

• VAT returns
• Payroll taxes
• Stamp duty filings
• Dividend Withholding Tax (DWT)
• Other periodic Revenue compliance requirements

Contact OSK Tax today for more information on key tax compliance deadlines.

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