Most taxes in Ireland work like this: the year ends, you work out what you owe, you pay. CGT doesn't. You pay first and file afterwards.
There are two windows in the year, called the initial period and the later period.
The initial period: January to November
Anything you sold from 1 January to 30 November is in this period. The tax on it is due by 15 December of the same year.
So if you sold shares in March, you have until December. Lots of time, which is exactly why people forget.
The later period: December
Sales in December get their own deadline: 31 January next year. Revenue splits it out because 15 December would be too soon for a sale made on, say, 28 December.
Filing: 31 October next year
Paying doesn't tell Revenue the details. For that you file a return. If you're PAYE only, that's usually Form CG1, or the CGT section of Form 11 if you're self-employed.
It's due 31 October of the year after you sold. Sold in 2026? File by 31 October 2027.
If you're late
The interest is small on a small bill. But it adds up, and the surcharge is on top. If you've realised you missed one, paying and filing now is cheaper than waiting.
- Late payment: interest of 0.0219% for every day it's late.
- Late filing: a surcharge of 5% of the tax if you're within two months of the deadline, 10% after that.
A quick calendar
Example
Sold shares on 10 April 2026 → pay by 15 Dec 2026.
Sold more on 20 Dec 2026 → pay that part by 31 Jan 2027.
File one CG1 covering both → by 31 Oct 2027.