Canberrans have been urged to check their lottery tickets, with one ACT resident taking home $4.8 million in Thursday night's draw.
The ticket, however, was unregistered, meaning lottery officials have no way of contacting the winner of the first-division prize to tell them the news.
The winning lottery ticket for Thursday's Set for Life draw was purchased from the Thistle Kiosk at the Westfield Woden.
The Canberran with the winning ticket will take home $20,000 every month for the next 20 years.
Thistle Kiosk owner Tania Dezman said she was excited with the announcement of the first-division win.
"It's fantastic news. We hope it makes a great change to the winner's life," she said.
"We can't wait to enjoy this excitement with our staff and customers.
"I hope our winner enjoys their prize and can start making plans."
Spokeswoman for The Lott Ally Ramsay said ACT residents who bought tickets for Thursday's draw should check their numbers in case they were a winner.
"Make sure you check your ticket, which could be in your wallet, handbag, fridge door or car glovebox because the winner could be you, and you could be planning what to do with your prize too," she said.
"If you discover you are holding the winning ticket, contact The Lott on 131 868 to begin the process of claiming your prize."
The winning numbers were 1, 17, 4, 25, 33 and 34, with the supplementaries of 39 and 18.