The Sindo piece is here (Third question) and although the author is a tax professional, I doubt if he is right.
His question is different from yours.
The father is giving the son a gift of €250k.
The son and his girlfriend are buying a house together.
There are two stages here.
If the father gives the son a gift of €250k, there is no CAT.
If the father gives them a joint gift, there would be CAT.
Stage 2
Son has €250k cash
Girlfriend has nothing.
They buy a house jointly.
If they own the house 50/50 , the the son has given his girlfriend a gift of €125k and it would be subject to CAT.
She gets €225k worht of house for half a mortgage of €100k
But my solution works.
He should own 250/200ths of the house and she should be responsible for the mortgage.
If they get married, he can then gift her half the house.
Practical considerations.
Relationships break down. They should have an agreement acknowledging the ownership.
Brendan