[For more current case annotated texts by this author, see Bernstein & Lookofsky, Understanding the CISG in Europe, 2d ed. (2003) and Lookofsky, Understanding the CISG in the USA, 2d ed. (2004).]
A. The Rule and the Exceptions
128. As noted previously with respect to the general Article 18(2) rule, an acceptance is not effective if the indication of assent does not reach the offeror within the time he has fixed or within a reasonable time. Article 21 of the CISG provides the following two exceptions to the rule: [page 75]
(2) If a letter or other writing containing a late acceptance shows that it has been sent in such circumstances that if its transmission had been normal it would have reached the offeror in due time, the late acceptance is effective as an acceptance unless, without delay, the offeror orally informs the offeree that he considers his offer as having lapsed or dispatches a notice to that effect.'
B. Notification by Offeror Accepting Late Acceptance
129. According to Article 18(2), a late acceptance is of no effect, and the offer to which the acceptance seeks to reply will lapse. However, under the exception set forth in Article 21(1), a late acceptance is nevertheless effective as such if the offeror promptly notifies the offeree to that effect. In such event, the acceptance becomes effective upon its receipt (and before the subsequent notice by the offeror).
C. Acceptance Timely in Normal Circumstances
130. Article 21(2) deals with a somewhat more complex situation: the late acceptance shows that it has been sent in such circumstances that if its transmission had been normal it would have reached the offeror in due time. In this case the CISG drafters chose to follow the Scandinavian rule:[l] the late acceptance is effective as such unless the offeror promptly informs the offeree that he considers his offer as having lapsed. [page 76]