Irish CGT deadlines for 2026 disposals: you pay before you file the CG1.
Miss the payment date and interest can start running, even though the return that reports the gain isn't due until the following year. This is the order it happens in.
The two dates that catch people out
You pay capital gains tax on Irish disposals in the same year you sell. You file the CG1 return that reports those gains the following year. Two dates sit months apart, and paying one does nothing for the other.
A worked example
You sell shares in October 2026 and make a gain. You pay the tax by 15 December 2026. You then file your 2026 CG1 return by 31 October 2027, nearly a year later. Paying in 2026 filed nothing.
Sell again at a loss in December 2026 and it changes your position for the whole year, so you may have paid too much in December. That December tax has its own date: 31 January 2027.
Initial period vs later period
Revenue splits the year in two. The initial period is 1 January to 30 November; that tax is due by 15 December. The later period is December alone; that tax is due by 31 January the following year. The return deadline is the same regardless: 31 October of 2027. It is never called a "2027 return".
If you made a loss or owe nothing
A return is required even if you owe nothing, including where losses or reliefs wipe out the gain. Filing the loss is also how you carry it forward against future gains, so it's rarely something to skip.
Records to keep
- What you paid for each asset, and when you acquired it.
- What you received on each disposal, and the date.
- Fees and costs on both the buy and the sell side.
- Opening holdings, if you held anything before your first export.
How CG1 Assist helps at both stages
One confirmed ledger drives both the payment calculation near the disposal and the CG1 return the following year, so the two never disagree. You confirm the interpretation once, and the deterministic engine does the arithmetic.
Coming soonThese are the general rules as we understand them, not advice about your situation. Check Revenue's own guidance and take professional advice if your case is unusual.