Ok, let's say you have 40K for 4 years earning 2% per annum.
So annually you get 800 Euro in interest and you pay 41% DIRT is 328 Euro.
So over 4 years you get an extra 1312.
That's if you are earning 2% and if you have 40K on deposit constantly. Which is not going to be the case, you'd only have as much as 40K in the year before purchase, and only for a couple of months.
I'm guessing for the borrower who starts out having to save say 10K per year, or about 1K per month it will be a lot less.
Take year one, 10K @ 2% = 200. Dirt is 82 Euro of that. I'm guessing for most people it won't even amount to 500 Euro.
However, if you are a wealthy first time buyer, say having a deposit of 100K over 4 years, it gets a lot more interesting.
How are they going to administer this