Suppose that you work in a company located in London. One day they send you to install some equipment in Manchester. The whole task takes one day and you return to London at the same night. They will pay you extra money for doing this job outside of your regular workplace.
1- What is this mission called? (I have seen the word posting but it seems to be used for longer periods of time like one month or more.)
2- What word would you use for the extra money that you will be paid for doing that task?