The National Lottery says the record-breaking €19.06m jackpot will be won on January 15th.
It says one or more Lotto players will get the current jackpot in a guaranteed 'will be won' event.
It follows criticism as the jackpot has rolled over since last June.
While a National Lottery spokesperson says if the jackpot is not won outright, it will be split.
"We know that most of our Lotto players would like to see the €19m jackpot won, so we are delighted to be able to make this announcement.
"On the night of Saturday 15th January, if the 'will be won' Lotto jackpot is not won outright, the full value of the jackpot prize will flow down to the winner(s) of the next winning prize tier."
Changes to future draws
While the Lotto operator says how jackpots will run in the future will also be changed.
It says the same 'will be won' event will take place going forward, with jackpots guaranteed to be won "no more than five draws after the cap has been reached".
The current Lotto jackpot has been capped at €19.06m since October 2nd.
Due to the cap, the additional funds allocated to the jackpot have been flowing down to the lower prize tiers.
The spokesperson adds: "Since the Lotto jackpot reached the €19.06m cap last October, we have seen winners at lower prize tiers benefitting from the prize roll down of approximately €23.9m - the biggest winner of all has been the Good Causes Fund which will benefit directly from €53m in funding from this Lotto roll cycle alone.
"Over the past number of months, we have worked with our technical suppliers and an independent review team to introduce this 'will be won' draw to the game.
"Following regulatory approval, we are delighted to be in a position to confirm that there will be a guaranteed 'will be won' Lotto jackpot on Saturday 15th January."