Get to grips with assumption agreements. This simple guide explains their purpose, key elements, and how they affect your business dealings.In real estate transactions, an assumption agreement allows a third party to "assume" or take over the loan of the property's seller. A person who assumes a mortgage takes over a payment from the previous homeowner. It allows one party to "assume" the rights and responsibilities of the other party. An assumption clause in a mortgage contract allows a home's seller to pass responsibility for the existing mortgage to the new homebuyer. An assignment and assumption agreement is a contract that allows one of the parties to transfer their contractual rights and duties to another party. The first step in creating an assignment and assumption agreement is to clearly identify the parties involved and their respective roles.