Does a deferred mahr (mahr was paid) need to be paid if wife never asks for khul'?

So a khula is when a wife requests a divorce and the husband agrees. In that situation, the general principle is that the husband will be entitled for his mahr to be given back. So in this case, if he never gave it in the first place, then he wouldn't need to give it. That's the general principle. Yes, there are certain exceptions, but that's the general principle in a khula. A husband would be entitled to his mahr back.