In general if the capital gain is below the personal allowance, there is no need to log it to the revenue , someone asked before.
See this article that I found: it explains some stuff in greater details. I'm not allowed to post links but if you search on Google you can see this recent article from Dominic Coyle in the Irish Times that explains this in grater details. Search it. It says
Turning to the kernel of your question, the answer is that you do not have to file a capital gains tax return if the gain you have made in the year is below the €1,270 exemption limit
I hope it helps
Malpes180