The Central Bank has formally turned the new mortgage lending rules into law with immediate effect.
Everyone looking to buy a home will have to save a 20% deposit first, unless they're a first-time buyer and the asking price is less than €220,000.
People who fall into that category will have to have 10% of the cost of the home saved first.
Prospective buyers will only be allowed to borrow no more than three-and-a-half-times their annual salary.
The new rules also officially ban lenders from helping customers get around the law.
The Taoiseach has said the new mortgage rules are designed to stop people buying homes they can't afford.
Critics say they will make it almost impossible for people in apartments to trade up to family-sized home, especially in Dublin where prices tend to be higher.
