You could sue your employer for breach of contract, to enforce the terms of the settlement agreement and get the money owed to you--the settlement is a contract, and its terms are enforceable in court.Alternately, their failure to pay, as a material (or significant) breach of contract would let you treat the settlement as terminated by their breach, ignore its terms, and sue them the same as you would had you not entered into a settlement at all. You have the option to sue to enforce the agreement or to treat it as terminated.The lawsuit to enforce the terms of the settlment is a quicker, easier, simpler one--all you have to show in court is the terms of the agreement and you have not been paid as per it. It is very straightforward.