I am looking for a slang word to describe the situation, where you are voluntarily working overtime at your job, but without getting paid.
E.g. if you stay late at your work because you would like to solve a specific problem; and you do that voluntarily with no pay because it is in your own interest.
It could also be the fact that you stay late to show your manager that you are willing to put down the work that needs to be done (perhaps so you may get a raise or a promotion in time); sort of an investment in your job.
Are there any fun or slang words to describe this?
In Danish we have the words "Interessetid" or "Interessetimer", which essentially translates to "Interest time" or "Interest hours".
Just for clarification, I am not referencing forced overtime. I am thinking about salaried work where in some industries it is common to work overtime - even though you are not getting paid extra to do so. Think about Banking, Consulting or legal work. In banking many people work maybe 60 hrs per week - even though their contract only states 40 hrs. Therefore the last 20 hrs. would be "voluntary overtime" (or the fun slang word I am looking for here, to describe this).