I acted as a courier once for Tara. I went to the other realm city deposited gold at bank. Not sure who got it, I think it went to the crown but I can't remember.
To be specific, I am pretty sure you have to go to the capital.
"In the central bank of Keplerstan, you can turn your gold coins into bonds transferable to any noble in their realm.
There is a flat 50 gold fee for this transaction, and you have to transfer at least 100 gold."
