Question

What does this expression mean if you take the king's coin you give the king his due?

Answer 1

The phrase is saying that in order to receive the money you should get, you should do the job you are expected to do. It is a expression.

Answer 2

The phrase or expression is meant to say that in order to receive the money you should get, you should do the job you are expected to do. Although the actual phrasing within the expression makes this a little difficult to understand this idea. In other words, you do the work, you get paid for the work you are expected to do.