Firm Offer(of a cargo or of a ship). A charterparty is a contract. An enforceable contract is formed when there is a definite or "firm' offer incorporating terms, and the offer is unconditionally accepted by the person to whom it is made. There are other requirements but for chartering purposes, for now, an offer and acceptance are analytical "tools" by which agreement is seen to exist or not. During the negotiations for a fixture offers are part of the negotiation process; an offer by one party, or his shipbroker, can be met by a counter-offer by the other side. A counter-offer is not an acceptance.