So, if you're sitting on a ticket you haven't scanned and you're from the City of Sails, it might pay to check your numbers.
And while $19.1m is only half of what could have been won, it's still a hefty pay-packet which could be used to splurge out on a great number of things.
Sure, you could go on a massive spending spree with your earnings but why not invest it? Photo / Supplied
Or, you could be clever with your cash and invest it where you could earn hundreds of thousands of dollars each year.
A spokesperson for Westpac said they'd recommend seeking independent financial advice to ensure it was invested in ways to reflect your savings goals.
That would likely include consideration of a range of options with higher earning potential, such as managed funds.
But assuming you would qualify for the bonus rate every month, you could earn over $300,000 in after-tax interest, the spokesperson said.
"Putting the full amount in our Westpac Bonus Saver account would earn $180,334 in after-tax interest in the first year.
"Putting $19 million in a 12-month term deposit and the remaining $142,857 in a Westpac Bonus Saver account would earn $345,056 in after-tax interest in the first year."