Three letters, and everyone assumes they're three versions of the same thing. They're not. One of them is the return where you explain your sales. The other two are just payment slips that tell Revenue what money is for what.
Once you see the split, the whole CGT paperwork thing gets simpler: one form with your numbers on it, and two chances during the year to hand over the tax.
CG1: the return
Form CG1 is where the details live. Every disposal for the year, what you sold, when you bought and sold it, what it cost you, the gain, your losses, the €1,270 exemption, and the tax you worked out.
If you're PAYE only, CG1 is your form. If you file a self-assessed Form 11, the CGT numbers go in there instead and you skip CG1.
It's due by 31 October of the year after the sales. Sold in 2026? File by 31 October 2027. Filing late brings a surcharge: 5% of the tax if you're within two months of the deadline, 10% after that.
CGA: paying the January-to-November tax
Payslip CGA covers the initial period: anything you sold from 1 January to 30 November. The tax on those sales is due by 15 December of the same year.
The payslip itself is just a payment slip with boxes for the amount and the year. It tells Revenue what the money is for. If you pay through ROS or myAccount, the slip is built into the online payment and you never see a paper version.
CGB: paying the December tax
Payslip CGB covers the later period: sales in December. That tax is due by 31 January the following year.
Same idea as CGA, different window. Nothing about the calculation changes. It's purely about which slice of the year the sale fell in.
Example
You sell shares on 10 April 2026 and more on 20 December 2026.
The April gain goes on a CGA payment by 15 December 2026.
The December gain goes on a CGB payment by 31 January 2027.
One CG1 return covering both is filed by 31 October 2027.
Paying and filing are two separate jobs
This is the part that catches people. You can pay on time and still be fined, because paying doesn't file anything. The CG1 is where Revenue learns what you actually sold, and it comes months later.
So the checklist is: pay by 15 December (or 31 January for December sales), then file by the following 31 October.
Which form do I actually touch?
- Filed a Form 11 before (self-assessed)? Use the CGT pages in Form 11. No CG1 needed.
- PAYE only? File Form CG1, usually online through ROS or myAccount.
- Everyone pays, whatever their form: CGA for January-to-November sales, CGB for December sales.
Short version
- CG1 = the return with your details, due 31 October next year.
- CGA = payment slip for sales from January to November, due 15 December.
- CGB = payment slip for December sales, due 31 January.
- Paying doesn't file. You owe Revenue both the money and the paperwork.