INTRODUCTION
In Part II of the CISG, entitled “Formation of the Contract,” the Convention provides the rules on contract formation, making reference to the model of offer and acceptance, provided in CISG Arts. 14 to 24. In the UNIDROIT Principles of International Commercial Contracts, the counterpart provisions on formation, also adopting the model of offer and acceptance, are located in Chapter 2, Arts. 2.1. to 2.22.
In both instruments the offer is defined and the relevant requirements are listed. In the Convention, the definition of and the requirements of an offer are contemplated in Art. 14. In the UNIDROIT Principles, it is Art. 2.2 that provides the definition of an offer.
DEFINITION OF OFFER
Article 14(1) of the CISG commences:
“A proposal for concluding a contract […] constitutes an offer […]”
Similarly, Article 2.2 of the UNIDROIT Principles provides a definition of offer, commencing:
“A proposal for concluding a contract constitutes an offer […]”
The concept of “offer” is the same in the two instruments, in the sense that both instruments conceive it as the invitation by one of the parties to conclude a contract; this invitation is accompanied by other requirements to which I refer in this comparative analysis.
The following difference between the counterpart provisions must, however, be noted: the regime of contract formation under the UNIDROIT Principles can be applicable to any type of commercial contract, whereas the Convention's regime is, in principle, limited to the formation of contracts of the international sale of goods (i.e., only contracts to which the Convention is directly applicable).