(a) This account must include amounts due the service company upon open accounts, other than amounts due from associate companies and from customers for services and merchandising, jobbing and contract work.

(b) This account must be maintained so as to show separately amounts due on subscriptions to capital stock and from officers and employees, but the account must not include amounts advanced to officers or others as working funds. (See account 135, Working funds (§ 367.1350).)