Acceleration clause is a term of a contract that allows one party to demand an immediate fulfillment of all obligations of another party in case this another party fails to fulfill one of the obligations or its part. For example, if party A must pay a certain sum of money to party B each month for 12 months in total and is able to pay only two first payments in time, but overdues the third payment, party B has the right to demand immediate payment for all the 12 months.