Abstract: In the increasingly prevalent context of marriage-like relationships, the determination of joint debts in creditor-debtor disputes between the parties and third parties significantly impacts the interests of all stakeholders. The rules for identifying marital joint debts serve four essential functions, which remain partially applicable despite the absence of formal spousal status in such relationships. Rather than outright denial, a functionalist perspective necessitates differentiated analyses: joint debts based on mutual expression of intent inherently bind parties across relational contexts due to their consensual nature; household daily necessities-type joint debts may only be recognized when creditors demonstrate reasonable reliance on the borrowing party’s ostensible marital relationship, the debt objectively serves household necessities, and creditors both knew of and relied on its conformity with such needs; while shared living or joint business operation-type joint debts require creditors to prove reasonable reliance on marital appearance, the debt’s objective allocation to shared living or business purposes, creditor awareness of its use, and the non-borrowing “spouse’s” actual or constructive knowledge of the debt coupled with failure to object. This framework ensures equitable burden-sharing while balancing legal coherence and relational realities.