The new 10% stamp duty won't apply to so-called cuckoo funds who rent the homes to councils.
It's after the government's proposal was passed in a Dáil vote last night.
The new tax was introduced in May due to concerns about institutional investors' bulk-buying homes, at the expense of first-time buyers.
A new bill that would give a legal basis to the controversial Shared Equity Scheme for first-time buyers will be debated in the Dail later.
The government scheme would see the State cover up to 20% of the cost of a new home.
However, opponents say it won't help bridge the affordability gap and will only lead to inflated house prices.