It allows one party to "assume" the rights and responsibilities of the other party. This type of agreement transfers the obligations of one party under a contract to another party.An assignment and assumption agreement assigns contractual rights or intangible personal property (such as intellectual property or goodwill) from one party. The general rule is that a contract is effective when both parties agree (ie, sign the Agreement of Sale) AND acceptance is communicated to the offering party. Mortgage assumption allows a buyer to take on the original loan balance at the original terms, but it doesn't account for any home equity the seller has built.