Married couples build and accumulate assets and liabilities -- what they own and what they owe. Liabilities come in many forms -- the balances on mortgages, home equity loans, student loans, car loans, money due any broker, unpaid utilities, property taxes, lines of credit. All of these must be satisfied, and the terms and conditions of this satisfaction are spelled out in the marital separation agreement. Any agreement a couple makes must conform to the laws of the jurisdiction in which they live.
Generally speaking, couples are responsible for all debts they contracted together and prior to the date of separation because the husband and wife have joint and several liability. After the date of separation, the new debts and liabilities of a divorcing couple belong to each of them individually.
A couple can get a very rough idea of the marital estate at issue by adding the sum of all their joint assets and subtracting that number from the sum of all their joint liabilities.
A couple who are separated on a trial basis are still liable for any joint debt each incurs individually.
Some liabilities can be handled easily. When a couple decides to divorce, joint credit cards should be satisfied and cancelled. The spouses will need to re-establish credit individually in any event. Spouses heading for divorce should inform their creditors, and put what is called a "hard close" on the accounts.
Other liabilities must be negotiated as part of the property settlement agreement and may require no spouse indemnifying the other.
A divorcing couple are liable for the debts they incurred when married, and if anything, their creditors are even more attentive to them than a stable married couple.