Translation:Shulchan Aruch/Choshen Mishpat/179

Paragraph 1- If an item is known to belong to the partnership, neither partner can obtain a presumption of ownership against the other. Even if it remained in his possession for a long time, a partner cannot say he purchased it from the partner or received it as a gift unless he brings proof. This is not just a case where it is known that each partner owns an equal share, but even in a case where people saw each partner bring money and invest with it and they were unaware how much each partner brought, and one partner subsequently produced the investment and said 2/3 belongs to him and 1/3 belongs to his partner, he would not be believed. Rather, they would split it equally. This is only where the partner is unable to claim the partnership was never created or that he returned the money, such as where witnesses saw the investment they had both contributed to in his possession. This is only prior to the division of the partnership. Once they have divided, however, they could obtain a presumption against each other.