I’ve been translating an Austrian case which came with a summary in English. Here, Geschäftspartner is translated as business partner. I am using the other party. I asked myself yet again if I am being too fussy here. In English, a partner is someone you work together with, either in a partnership or on some kind of venture, whereas Geschäftspartner in this case means the other party to a contract. Of course, the other party is a more cumbersome expression than business partner, but at least it makes sense.
I had a brief look in Google, and I found support for my point of view. There was a partner on a Netherlands site, and some British sites given advice on partnership. I didn’t look very long.
I consulted some EU sources and found three hits for counterparty. That was new to me. But I discovered it has a specific meaning in business, in swap contracts.