Word or term comprising payor and payee

I am looking for a word or term that encapsulates both the payor and payee. ideally it would be used in a bookkeeping context.

Example:

Company X both receives and and sends payments to company Y. In the bookkeeping transactions they are ....

Please, do not feel limited to the example given.

Though I agree that parties is the generally used hypernym, another term you can use is transactors.

ODO:

transactor NOUN

Example sentences:
‘Better information improves markets by permitting transactors to make more informed choices.’
‘Only an eighth of the transactors are in the public service: their numbers have been growing slightly more slowly than those in the private sector.’

transact VERB
[WITH OBJECT] Conduct or carry out (business)
‘traders transact business in the public exchange’
[no object] ‘the dealer must know the price at which he is prepared to transact’

a word or term that encapsulates both the payor and payee.

I believe that would be party or party to transaction.

party a person or people forming one side in an agreement or dispute : a contract between two parties.

The New Oxford American Dictionary

party to the transaction - a party of people taking a role in legal proceedings

The Free Dictionary

payee - Party to whom a bill of exchange (such as a check or draft) is made payable.

Business Dictionary

A third-party transaction is a business deal involving a buyer, a seller and a third party.

Investopedia

The party issuing a check is called the payor (in legal parlance) or the payer (in common communication). The party whose name appears on the check or to whom the check is issued is called the payee.

Bookkeeping