It allows one party to "assume" the rights and responsibilities of the other party. An assumption agreement is a kind of legal document that you'll find commonly used in finance and real estate transactions.Assignments and assumptions are part of contract law and refer to the transfer of someone's duties and benefits in a contract to another. In real estate transactions, an assumption agreement allows a third party to "assume" or take over the loan of the property's seller. An assumption agreement also allows the party retaining the house to keep the existing loan rate, repayment period, principal balance, and other terms intact. Assuming a mortgage in a divorce means taking over the existing mortgage on your marital home solely in your name. The Parties agree that this Assumption Agreement and the actions to be taken as contemplated herein shall constitute the first such sale or exchange. 21.