The Guardian reports her salary is more than 1300 times higher than the UK prime minister's.
But despite that staggering fortune, Ms Coates is relatively unknown in the UK and around the world.
Ms Coates, a former betting cashier who previously worked for her father's betting company, started Bet365 in 2001 in a temporary building in a car park after graduating from Sheffield University with a degree in econometrics and buying the Bet365.com domain on eBay for £19,000 (NZ$35,900).
Today, along with brother John and father Peter, the family has an estimated bet worth of £5.8 billion (NZ$10.9b) thanks to the soaring popularity of online gambling.
But Ms Coates' massive wealth has attracted its fair share of controversy.
High Pay Centre director Stefan Stern told The Guardian last year the mother of five's pay was a "ridiculously massive sum of money" — especially because it was earned from the suffering of many, given the high rates of gambling addiction around the world.
"When a business is making its money in a way that causes a great deal of concern about its level of social responsibility it is even more unacceptable to see someone extracting this amount of wealth while so many people are left as victims in the wake of its business operations," Mr Stern said.
"Business does not operate in isolation from society.
"They shouldn't be able to get rich while effectively creating massive social problems for the rest of us, who have to pick up the bill for the social cost of people broken by their commercial success."
The 51-year-old lives a quiet life away from the spotlight in a farmhouse in Cheshire, England with husband Richard Smith and their five children, four of whom were adopted from the same family in 2014.
She is known to drive a luxury Aston Martin with personalised number plates which bear her initials.
She is not active on social media and rarely gives media interviews, although she has been honoured for her service to business and the community as well as being named as one of the most powerful women in the UK.
In 2012 she established the Bet365 Foundation, later renamed the Denise Coates Foundation, which has donated more than £100m (NZ$189m) to charities such as Oxfam.