Eager punters are expected to spend more than €250,000 an hour in the peak buying time from 4.30pm today until the tills close for the draw.
They will be buying more than 1,000 tickets every minute and spending an average of €4.50 each on their chosen combinations.
Two weeks ago 49 Lotto players were just one number away from a winning combination to hit the jackpot. One of them matched five numbers and the bonus and came away with €25,000.
A lucky couple from Co Kildare last won the jackpot, when they scooped more than €4.6m.
If it is won tonight, the winner will join an exclusive club of 452 Irish Lotto millionaires. An estimated 70pc -- more than 300 of the country's Lotto millionaires -- have opted to keep their identities a secret.
While winners will still be able to keep out of the public eye, new powers will give social welfare inspectors the right to find out if Lotto jackpot winners are still claiming the dole.