This type of agreement transfers the obligations of one party under a contract to another party. A person who assumes a mortgage takes over a payment from the previous homeowner.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 is a legal document through which one party transfers its obligations or duties under a contract to another party. It allows one party to "assume" the rights and responsibilities of the other party. An assignment and assumption agreement is a contract that allows one of the parties to transfer their contractual rights and duties to another party. An assumption clause in a mortgage contract allows a home's seller to pass responsibility for the existing mortgage to the new homebuyer. A provision in the terms of a loan that allows the buyer to take legal responsibility for the mortgage from the seller under certain conditions.