What is a legal document that makes someone responsible for another person's debt called?

A surety agreement is indeed the legal document that makes one party responsible for another person's debt. In this type of agreement, the surety (or guarantor) pledges to cover the debt or obligation of the original borrower if that borrower defaults or fails to meet their financial commitments. This arrangement provides additional security to creditors because they have more than one source to recover the owed amount.

Understanding the significance of a surety agreement is crucial in various financial transactions, particularly in situations like loans or rental agreements, where a party may need additional assurance that the debt will be settled. This type of agreement is typically a written contract that specifies the terms of the obligation and outlines the liabilities of the surety in relation to the primary borrower.

The other options provided do not function in the same way. Promissory notes document a loan and the borrower's promise to repay it. A bond is generally a debt security that represents borrowed funds that must be repaid with interest. A mortgage is a specific loan used to purchase real estate, secured by the property itself, rather than making someone responsible for someone else's debt. Understanding the distinct roles and implications of each type of document is essential in the context of financial obligations and liabilities.