As a job seeker in Australia, when a recruiter or job agency ask me about my minimum expected salary, I wonder how to express the salary figure in a natural way. For example if I look for $120,000 per year should I say: "one hundred twenty K", "one twenty thousand" or ...? should I always say the currency (dollar) or it's not required as certainly I mean Australian Dollar?
There's a lot of different ways you can write $120,000. As long as your point is clear, they're all acceptable. It's important to note, however, that different notations convey different levels of formality. 'One twenty K,' for example, is acceptable when speaking colloquially, but looks dreadful when written. Furthermore, more formal engagements would necessitate a construct such as 'One hundred and twenty thousand.'
Written forms necessitate even more variation. I follow the general MLA guidelines when writing numbers outside of a physics/math context: If it can be spelled out in one or two words, write it. Otherwise, use numbers. Here's a handy blog post on the subject.
As a general rule, though, use whatever you feel like. There's not really a well-defined 'best' answer, it's simply whatever fits the best with your style of writing. That being said, I tend to see the form '$120K' used disproportionately often in income-related things.
I'd sound a bit formal as it has to do something with my job, my living! That said, I may not prefer saying 'k' for a thousand.
Natural way could be:
(one) hundred and twenty thousand (dollars) per annum.
I would certainly include 'per annum' to avoid confusion. Yes, the word 'dollar' is optional as both of you are talking about Australian Dollars. This is quite equal to I getting a call from a job agency and replying 'Six Lakh per annum.' Since we both are Indians, I don't need to mention 'Lakh is Hundred Thousand' and of course, the figure is in Rupees.