With an eye-watering $20 million Powerball jackpot up for grabs tonight the secret to sanity and happiness might lie with a cheeseburger to celebrate and back to work on Monday.

Many fantasise about early retirement and splashing out on cars and houses but in reality most big winners return to work and get plenty of advice before spending.

A Kaikoura couple who won $8.6 million in 2014 said they "could count on one hand" the number of people they told - and that included their children, bank manager and lawyer.

The grandparents celebrated their win with a cheeseburger and fries at McDonald's and said returning to work kept them grounded and happy.

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"We found that working was one of the best ways to help keep things feeling normal and still enjoy working two years on from our win," the woman told the Weekend Herald.

The pair had helped their children financially and set up education funds for their grandchildren but had only just booked a long awaited European holiday.

"My husband and I always dreamed of going to Europe, but it always seemed like a bit of an impossible dream... until now, that is. We can't wait to soak it all up," the woman said.

The couple, who still want to remain anonymous, said despite not spending up large the money in the bank had "brought the colour back to their lives".

There have been iPads and treats for the grandchildren and the financial security of being able to help their children had brought them closer as a family.

"Just knowing we had the winnings in the bank and could help our kids out took so much pressure off us - we feel like we can relax and have a bit more fun."

The pair have also given to charities such as Surf Life Saving New Zealand.

Despite their multimillion-dollar windfall the couple still occasionally buy a Lotto ticket.

"Every now and again, we pick up a ticket and have a secret giggle to ourselves when they wish us good luck. Who knows, lightning could strike twice."

The couple said anyone lucky enough to win tonight should surround themselves with good advice.

"Listen to your partner, kids and friends, and professional advisers like bank managers and lawyers. It's a massive change to your life and they're there to help you make the most of it."

Lotto New Zealand said there was no secret formula to winning big - apart from buying a ticket.

"Due to the entirely random nature of lottery games, there are no strategies that can increase a player's chances of winning," said Emilia Mazur.

"Every line on every ticket purchased has exactly the same odds of winning."

The organisation has however released a list of lucky Lotto shops throughout the country.

The biggest single wins are:
• $36.8 million Big Wednesday win in June 2009 from Kuripuni Lotto & Post Shop in
Masterton
• $33.0 million Powerball win in September 2013 from One Step Ahead Auckland
• $28.7 million Powerball win in September 2010 from Mobil Papakura Auckland
• $27 million Big Wednesday win in September 2012 from AJ's Lotto in Tauranga
• $26.5 million Powerball win in March 2012 from Te Kauwhata Four Square

There are currently two major prizes that remain unclaimed:
• $200,000 Lotto First Division prize won on a ticket sold at Pricecutter Four Square Raetihi in January
• $200,000 Lotto First Division prize from a ticket sold at Paremata New World in Porirua in May