Section 23 is the original name for this relief which goes back about 20 years, can't think of current section it falls under but you can claim it even under afforadable housing - it's called owner occupier relief. If you check www.revenue.ie and search owner occupier they will give you exact computation. Normally you can gain between and extra 1600 - 3200 in tax credits and an additional srcop of between 4000 - 8000. These figures depending on cost price of house/apt to build, site cost and sale price. Good luck with your decision.