If my mahr was stated in a different currency, do I pay it back in the original currency after khula?

So anytime you're dealing with differing currencies if you have access to the original currency, you are permitted to pay it back in the original currency.

If it is in a different currency, then you should do the conversion from the original currency to the currency that is available to you on the day that you're going to pay it back or on the day that the khula is agreed to.

So let's say for example, you were given $10, 000 Antarctican dollars.

And the conversion is two to one to American dollars.

You do the conversion on the day of your khula and the mahr that you would return would be $5,000 American dollars.

Anytime you do currency conversion or currency exchange, it has to be done on the day of payment.

Why?

Because you want to avoid fluctuations, arbitrage, and thus dispute because of the differing amounts.