Economic analysts estimate the average Australian employee works more than four-and-a-half unpaid hours every week.
National "Go Home On Time Day" is a campaign aiming to highlight the amount of unpaid overtime worked in Australia.
Analysts at the Australia Institute say it's time for workers to stand up against what it calls the "theft" of their time.
On National Go Home On Time Day, employees are urged to finish work as soon as they've completed their paid hours.
Jim Stanford, director of the Institute's Centre for Future Work, told the ABC the scale of the unpaid overtime worked is astonishing.
"Each year, we do a big survey and ask how many hours you work, how much you get paid for, how much unpaid overtime are you doing in all the different forms - checking emails in the morning before you go to work, working through lunch, staying late without getting paid, checking emails and returning calls when you get home. On average, for employed Australians, they're working about 4.6 hours of unpaid overtime each week. That adds up over the year to 14 per cent of all the time you get paid for. So you think about it, Australians go to work and get paid, they are working another 14 per cent for their employers without payment."
It adds up to 48 million unused leave days a year.
In addition, Jim Stanford says, around a third of Australians aren't entitled to paid annual holidays.
"Duress can come in various forms."
Of those that are, around half don't take their full leave entitlements citing work-related pressure or job insecurity.
"Some of them are saving it up to use later so both on a day-to-day basis, work is creeping into our leisure time and even that one chance of the year to get away, recuperate with your family and put the sausages on the barbie and everything else - that's now in jeopardy as well."
The campaign is supported by the Australian Council of Trade Unions.
President Ged Kearney has called for workers and their bosses to take a stand.
"Well I think the Australia Institute have estimated over $100 billion is worked in unpaid work every year. That's an extraordinary amount of money that people are giving to the economy for free, it's not going back into their pockets, so we have to really put some constraints around work hours, we have to fight really hard for people in these causal and precarious work situations to get paid leave so they can actually have a holiday and we have to work really hard for people to get paid for the work that they do. Bosses need to stop asking people to do that extra for nothing."
The ACTU boss says it's also a safety issue.
"If you are working really long hours, depending on your job, you can get very fatigued and when you get fatigued you make mistakes, and when you make mistakes you can actually get hurt, not to mention your mental health."
Jim Stanford says, in general employees aren't staying back voluntarily but are under pressure - implicitly or otherwise - to work unpaid hours.
"Duress can come in various forms. It may not be the boss pointing the finger at you and saying if don't stay late tonight you are fired but it does come in different implicit forms: the expectation that, you know, you won't get your promotion, you might not be around that long unless you show that work ethic, especially given the large number of Australian workers who don't have a permanent job anyway, they are casual. So that's where the fear that you're going to be out the door if you don't impress the boss is that much stronger."
The Business Council of Australia says it supports a healthy work-life balance, and workers and bosses should negotiate leave so it is convenient for both.
