The Act and rules state that it is the responsibility of the lawyer to deal with funds under the control of the law practice in accordance with the instruction of the person on whose behalf the money is held, unless otherwise required by law. That person is not always your client.
You should provide each person with a complete and understandable statement of all trust money received, held and disbursed. Costs cannot be taken from joint money without authorisation of both parties.
Know the person for whom you hold the money