When two individuals work together within a business that they co-own, they are called "business partners". When you are one of those individuals, you would call the other person "my business partner".
But let's say we have two limited liability companies (or at least, organizations that are not seen as identical to the owner, and would be referred to by the name of the business rather than the owner as an individual). And let's say these companies do close business together. For example:
An import company that works together with the same manufacturer for a long time.
A store that always uses the same marketing company for advertising.
What would one of such a company call the other? e.g. could such an import company refer in their official documents to that manufacturer by "our business partner"?