The original section on this is section 603A Taxes COnsolidation Act 1997. Originally intended to enable parent to gift a site to a child for the purposes of the child building their principal private residence. Value limit of €254,000 applies. Finance Act 2007 has now brought in an area limit also of 1 acre exclusive of the site of the house itself. This was to stop perceived misuses of the system where someone could have transferred say 10 acres at 25K per acre in value to the child and the parent avoid CGT and the child avoid CAT.
If the child disposes of the site and it does not at that point contain a dwelling which was constructed by the child on it and occupied by the child as their residence for 3 years, then the tax which would have accrued to the parent (CGT) falls due on the child.
It is a very valuable relief as long as the conditions are adhered to. One should therefore ensure that all conditions are met by getting appropriate professional advice at the time the transaction is going through.
As previous poster has said, as the area is 3 acres, it depends on whether this is caught by the FA 2007 changes or did it go through before that. Check with solicitor and be sure they are aware of the CGT/CAT reliefs being claimed.