Well ... no difference unless the offeree pays for irrevocability, since in that event the offeror’s promise not to revoke is ‘supported by consideration’ (and therefore binding). Furthermore, even absent consideration, the offeree’s reasonable reliance can render even a ‘naked’ offer binding under American domestic law. 941941. § 90(1) of the American Restatement (Second) Contracts provides: ‘A promise which the promisor should reasonably expect to induce action or forbearance on the part of the promisee or a third person and which does induce such action or forbearance is binding if injustice can be avoided only by enforcement of the promise ...’.
Beyond these caveats (exceptions to revocability), the knowing American student might also add that, as regards sales of goods, State statutes have largely displaced the traditional Common law rule. The model for these statutes is § 2-205 of the American Uniform Commercial Code (UCC), which provides:
An offer by a merchant to buy or sell goods in a signed writing which by its terms gives assurance that it will be held open is not revocable, for lack of consideration, during the time stated or if no time is stated for a reasonable time ... 942942. Provided such period of irrevocability does not exceed three months. See UCC § 2-205. According to case law, a substitute for a signed writing (e.g. an email) will do. In New York, for example, an unsigned but ‘reasonably authenticated’ writing assuring that an offer will remain open is not revocable for want of consideration.
Therefore, when it comes to the single most important contract type, we might boil the key difference between American and Danish law on the revocability issue down to this:
Under American law, an offer to buy or sell goods is not binding unless the offeror clearly wants it to bind, whereas under Danish law, an offer is binding unless the offeror does not want it to bind.
Hardly a big difference, but a difference nonetheless. In fact, since the difference between American and Danish domestic law on this point reflects corresponding differences between other (e.g. Common and Civilian) jurisdictions, 943943. Re. the essentially similar approach shared by Civilian systems, see Hugh Beale, Bénédicte Fauvarque-Cosson, Jacobien Rutgers, Denis Tallon and Stefan Vogenauer, Contract Law: Ius Commune Casebooks for the Common Law of Europe (2010), Part 6.2.B (Revocability of an Offer). the adoption of a harmonized rule for inclusion in Part II of the 1980 Vienna Convention on Contracts for the International Sale of